Technical Report N o . 29 A REPRODUCTIVE BIOLOGY AND N T R L HISTORY O T E AUA F H JAPANESE WHITE-EYE (ZOSTEROPS JAPONICA JAPONICA)
I N URBAN O H AU
Sandra J . Guest Department of Zoology University of Hawaii Honolulu, Hawaii
ISLAND ECOSYSTEMS I R P
U . S. International B i o l o g i c a l Program
September 1973
Table of Contents Abstract
List of
................................................iii Tables .......................................... v
List of l l l l u s t r a t i o n s
Introduction
The White-eye
................................... ............................................ 1 ............................ 1 in
Hawaii
vi
............................ 3 Materials and Methods ........o........................... 5 Sanding ............................................ 5
The Vhite-eye elsewhere Determination of Territory and Population Song
.~..................~..........e............... 7 The 9 e s t ........................................... 7
The Egg
.......... 6
..................e.................l....... 8
Eeasurements of Young and A d u l t s
A v i a r g Techniques
................... 8
%stilts and Discussion
-Population and Study Area General Seasonal Cycle
sound Production
T e r r i t o r i a l Behavior
Courtship. Copulation. Nest
.................................11 .........................11 ............................ 11 ..................................16 ..........................,.,. 21 and .... 27 .....................,..................
Nest S i t e Selection
28
.................................. 9
k c a t i o n of ?Jests Vest Construction Spacing of >jests
.................................36 ..........................,,...... 37
...................,..,............
31
Description of E g ~ s
C l u t c h Size
.........................e.....41
............................I....,..... 41
ii
Laying. Pipping. a d Hatching
Ageing of Eggs
...................
43
..................................... 43 Incubation Period ....................... ....@*,. .. 46 NestEng Period .................................... 46 Nest Attentiveness .........................See....e 48
Feeding of 3iestlings
Developnent and Growth Nest s n i t a t i o n
Fledgling Wriod
Breeding Success
............................. 57 .................................... 63 .................................... 63
................................... 65
72 7$nite-eyes
............................... 53
General Eehavior
........................ .....................74 of .................................82 Mult Diet ...........................e................... 234
Sunmrary of Breeding Success
Ilales,
Chisholm (1932)four-d q r e a t s i m i P i a r i t i e s i n size, shape, s t r u c t u r e ,
-4n e s t building, egg color, and general h a b i t s of - l a t e r a l i s and 2. Z.
halmaturina.
Only the plumage c o l o r varies.
O t h e b a s i s of body n
dimensions, four fomer African spscies have been reduced t o two species ( ~ l a n c e y ,1967; Foreau, 1957).
And within one species in Few Zealand
(2,l a t e r a l i s ) ,
Marples (1945) was a b l e t o seperate nine categories on
t h e b a s i s of b e l l y color. Skead (1967) explains t h i s confusion i n c o l o r v a r i a t i o n by discussing t h e two groups of pigments involved: carotenoid and melanin. Both types
a m f o d in each f e a t h e r i n varying proportions.
Abrasion, type of
melanization, and humidity seem t o a f f e c t t h e f i n a l appearance of color. Furthermore, it has been reported t h a t a t l e a s t one species of White-eye
(2.
japonica) becomes darker when i n c a p t i v i t y (Insram, 1908).
This is
a l s o t r u e of o t h e r species of b i r d s (Bent, 1 9 8 ) .
Whatever t h e reason,
c o l o r v a r i a t i o n has caused a g r e a t d e a l of confusion i n c l a s s i f i c a t i o n of t h e 200 forms of the Zosteropidae; only 80 species a r e now recognized. The taxonomy of t h i s group i s s t i l l far from being worked out completely. Even t h e more recent works, which a r e based on body dimensions
instead of plumage color, may be misleading, and behavior and ecology should be studied before f i n a l taxonomic decisions a r e made. Yarrison
(1958) has shown t h a t two morphologically similiar species in western
2. l Australia (2. l a t e r a l i s and - -u t e a ) a r e ecologically very divergent.
AU. of t h i s points t o the f a c t t h a t more
of t h e world.
work i s needed on t h e Zosteropidae
-5Naterials and Methods For the most p a r t , t h i s paper i s based on f i e l d observations, However, t h e r e were c e r t a i n techniques which were employed t o c o l l e c t data, These are outlined.
Banding
A l l b i r d s banded on campus were baded with a U.S. Fish and ItildlFfe metal band and two o r three p l a s t i c bands i n d i f f e r e n t c o l o r combinations, s o each bird could be recognized a s a n individual, ' I used a mist net t o capture t h e b i r d s (see Low,
1957). For %hite-eyes, t h e b e s t method
i s t o place t h e net low t o t h e groturi, i n f r o n t of a bush f o r camouflage,
I used two techniques t o n e t birds.
The first technique requires stuqying t h e f l i g h t paths of b i r d s i n one a r e a , near a feeding o r bathing l o c a t i o n where l a r g e numbers of b i r d s congregate, and then placing t h e n e t across one of t h e paths. d i d not leave t h e n e t unattended, and removed t h e b i r d s immediately. A second technique i s t o t r a p t h e parent b i r d s a t t h e i r nests. n e s t l i n g o r fledgling i s placed on the ground, b e M t h e net. parents then swoop over t h e chick, and i n t o t h e net. The
A
I
If t h e a d u l t s are
h e s i t a n t , t h e chick may be dropped t o t h e gmund, and a s it f l u t t e r s down, the adults
w i l l f l y with it i n t o t h e n e t (see page&).
A variation
of t h i s technique t h a t i s very successful, i s 'to place an a d u l t in a cage behind t h e net. net. Other White-eyes w i l l become curious and fly i n t o t h e
I a l s o banded young b i r d s i n t h e n e s t , o r on t h e day of fledging,
It i s b e s t t o band them on t h e eighth day a f t e r hatchin?, o r on t h e day
of fledging.
If older t b n e i g h t days, they ~~6l-l the n e s t prematurely, leave
and if older than 10 o r 11 days, they become r a t h e r difficult t o catch.
-6Birds were sexed by behavorial differences l a t e r i n f i e l d observations.
I recorded weights of some birds, molt, and general condition
N attempt was made t o recapture individuals, o
of b i r d a t time of banding,
but a record uas kept of f u r t h e r sightings.
A funnel t r a p as described by Cunningham (% 1)
was unsaecessful.
was used, but it
Determination of Territory and Population There a r e various references t o mapping t e r r i t o r i a l boundaries, but many seemed unsuited f o r Flhite-eyes because aggression i s often seen in t h e f i e l d but not a t well defined boundaries between t e r r i t o r i e s .
This also i s true of other species of Zosterops (~lerrrming, 1 9 2 ) .
I
d i d not see a c t u a l boundary defense in enough instances t o successfullg map even one t e r r i t o r y completely. Also it i s d i f f i c u l t t o i d e n t i f y
irrlividuals, even when banded, because t h e birds are very a c t i v e and move rapidly in the f o i b g e . For this reason a technique such a s
described by Odum and Kuenzler (1955), where individuals are i d e n t i f i e d i n d i f f e r e n t parts of t h e i r t e r r i t o r y and the lines of boundary drawn according t o where the bird spends the majority of time, is not applicaple. Eowever, the males do sing f o r a period of 20 t o 40 minutes a t sunrise, and I used this t o determine t e r r i t o r y . The approximate t e r r i t o r y boundaries were measured by finding song positions of the males during the early morning singlng.
This
the
was done early i n the season t o elinrinate the chance t h a t juveniles
might be singing. positions.
I then divided the area evenly between t h e song
Since the song positions change durin? t h e season, a l a t e r
mapping would show s l i g h t l y different t e r r i t o r i e s .
-7-
I feel that this is a fairly accurate technique in that, where
territory defense
was
observed, it correspnded roughly to the bomdarg
lines, and the lines tended to fall along n a t d boundaries (i.e., tall buildings, open areas)
.
Each territory was ranked by size.
Size was determined by cutting
out a figure of the territories from a map and weighing the paper. Forty-two territories had all four boundaries mapped, and every f o u r t h one was examined for the vegetation present. then compared to territory size. estimated by a s sSong
To study the singing cycle, a transect of about
The vegetated area was
Tne total population (resident) was
a pair of birds for each territoly.
9266 meters was
laid out across campus.
I walked it at an even pace (total time about
30 minutes), at various times of the day and noted the number of songs
heard. From this information, I determined the relative amount of
singing at different times of day.
Any time
a song was heard during the season it was also noted, and
this bird.
was
compared to the stage of the nesting cycle of the singing
This yielded a rough estimate of when sirnging occurs during the
individual cycle. The Nest Certain measurements were taken at the nest. Hei5ht was measured from the
bottom of the nest to the ground directly belox the nest, tJith a tape measure.
In certain instances, I measured height as the distalzce from
Distance from the edge
the bottom of a nest to the roof of a b u i l d i q .
of the nest to the end of the nest limb, the distance from the nest
-8t o t h e base of t h e t r e e , cup depth, cup diameter,
rim thickness,
bottom thickness, and diameter of branch where nest i s attached were a l s o measured (see fig. 1 ). t o t h e n e a r e s t 0 1 mm. . Several n e s t s were c o l l e c t e d ard placed i n a Tiilkpen funnel, and
A s a r u l e these were measured in milimeters ,
04 t h e fauna preserved i n 7 5 alcohol.
Lice a d i n s e c t s were mounted
in
Hoyers Solution and incubated a t 4 0 ' ~ . f o r two weeks.
I recorded whether t h e n e s t s were on t h e 1eewai.d o r windward s i d e
of t h e t r e e . I n t e r s p e c i f i c and i n t r a s p e c i f i c spacing of n e s t s was
measured by marking t h e n e s t s on a map and measuring distance, o r w a s
determined d i r e c t l y d t ' n a tape measure i n t h e f i e l d .
The
Eggs were weighed on consecutive days durhg t h e 1972 season
s e v e r a l nests.
at
Air c e l l diameter was measured on consecutive days(fig, 2).
Clutch s i z e s were noted. Measurements included t h e longest and widest dimensions of t h e
egg measured t o t h e nearest 0.1 mm, and t h e long diameter of t h e a i r c e l l t o t h e nearest 0.1 m , with c a l i p e ~ s . Weights xere taken a t t h e n e s t with Pesola scales (accurate t o 0.1 gms) , Color was recorded.
See
Figure 2 f o r more d e t a i l .
Keasurements of Young and Adults Several measures were taken on developing birds.
They were -mighed
. on consecutive days with h s o l a s c a l e s , t o t h e nearest 0 1 gms.
For
information on f e a t h e r t r a c t d e v e l o p n t , pictures and sketches were loade a t t h e nest. Feasurements of adult b i r d s fd.men length, tarsus l e n ~ t n ,win- and
-9t a i l lengths) all a r e as described by P e t t i n g i l l ( 9 7 ) 1'0.
Aviary techniques
1 maintained an aviary of 8 f t . x 6 ft. x 4 f t . f o r 18 months.
Adults were fed honey-water
and vitamins, c e r e a l , oranges, apples, and
one s o f t fruit every day (see B d i n g e r , 1969).
F r u i t was usually hunz
in t h e cage, r a t h e r than crushed in dishes.
Several birds were hand raised, a d c e r e a l , vitamins, egg yolk, f r u i t ,
and honey comprised t h e m a i n d i e t .
The yow
were fed every 1 0 minutes
a t fledging, o r xhen they called f o r food.
rim thickness
cup diameter
cup depth
\
I
.I
tree base
to
b o t t o m depth
Figure 1.
Measurements of the Nest.
Figure 2,
Reasurements of the Egg,
Results and Discussion Population and Study Area The study population i s located on t h e University of Hawaii Manoa campus.
It i s an open a r e a , with a large number of c u l t i v a t e d t r e s s
The m a i n
and shrmbs, ard i s somewhat s i m i l i a r t o a r e s i d e n t i a l area.
campus covers 83.5 a c r e s , and includes approldaately 52 breeding pairs of White-eyes. This gives a n average of 0.62 pair per acre, and a
d e n s i t y of 124 b i n i s per 100 acres,
Kikkaua (1962) f o u d 2. l a t e r a l i s
1
-
t o have a density of 1.2 pair per a c r e i n a wooded area in I?ew Zealand. General Seasonal Cycle
Breedb~ seasons may be initia;td by various f a c t o r s (food supply,
preciptation, increase o r decrease of day length;
Van Tgne and Berger,
191).
In t r o p i c a l areas t h e problem of determining what i n i t i a t e s t h e I n Hawaii, t h e
season i s complex, and s e v e r a l f a c t o r s may be involved.
nesting o r breeding season s t a r t s in Januarg o r February, and t h i s correspords t o t h e w e t t e s t period of t h e y e a r 1972).
lumenst stock
and Price,
This suggests t h a t t h e r e may 'be a c o r r e l a t i o n between rainfall
and i n i t i a t i o n of the breeding season. There i s one r e p o d that t h e breeding season of mite-eyes in
Hawaii extends from February through Rovember (Ord, 1971), b a t he s t a t e d
r (personal coraamtnication) i ! June of
1973
t h a t he did not f e e l t h e
ng season was that long.
I?n both 1972 and 1 9 3 , I found
t h e earliest. s i g n of nesting in January and the first n e s t with an egg
i n February.
The season extends to July.
Since the r a i s i n g of a
complete brood takes about 50 days, a single pair may z i s e as many as t h r e e successfd. b r o d s i n one season. completed three successful broods, I n 1972, a t l e a s t t-.TO pairs
An annudl molt begins in l a t e July o r e a r l y August, but one bird
w s feud moltin5 during the summar. a
Z, T o molts a r e present i n w
lateralis a
in Nw Zealand ( ~ k i r p l e, 1945), so a second molt in Z. e s
i s possible.
2,
Flocks a r e comon during the nonbreeding season.
Large flocks
(I saw one of over 100 b i r d s a t Diamond Head during t h e summer of 1972)
m y be composed m a i n l y of juveniles. a
l reason f o r t h i s statement v
is
that several known banded pairs were seen i n small f l o c k s near t h e i r
tcerritoqy throughout t h e summer of 1972.
One p a i r was never seen with
more than e i g h t t o t e n b i r d s , a d always together within the small
f l o c k s (observed more than t e n times). Winter f l o c k s begin t o form
in July and begin t o d i s i n t e g r a t e i n Januarg and Febmxarg, when
territo~g establishment an$ defense begins,
This pattern i s similiar
t o o t h e r species of W t e - e y e s (Cunningham, 1g4-6a; b r p l e s , I*).
In cornparkg the 1972 and 1973 season, t h e 1973 season was about
two weeks l a t e r than t h e previous season.
I have some evidence suggesting
evidence for
a t h a t i n 1973 t h e r e m y have been less f a d available.
t h i s i s based on some observatLons of fnch woms ( b p i d o p t e r a , ~ e o m e t r i d a e ) ,
a very common food sf t h e White-eye.
In 1972, while searching for nests
I had occassion t o move through very t h i c k Haole Koa (Leu, L ~ e n a ' leucocew),
After emerging f m n t h e vegetation I could e a s i l y -pick
z d o f f m clothing. m y
10 t o 15 larvae out sf ny h a i r
In 1973, I walked
through t h e same stand of h o l e Koa, and spent about t h e same amount of time i n t h e f i e l d , and did not fiml more than one inch w o n a t a
time on my body.
This suggests t h a t t h e food nay have been less
Them
abundant, and might explain t h e later s t a r t Lo t h e 1 9 3 season.
k-as a very severe %fi?Itsr drought i n 1972-1373 t b a t could have affected
-13the abundance of food.
Skutch (1950) found thzt i n Central America
t h e period of g r e a t e s t food abundance c o r r e l a t d with t h e time when
809 of t h e species nested (van Tyne and Berger, 191), s o t h e abundance
of food availability may influence the start of the season.
-14Table I Calendar f o r 1972-1973 Floclrin,~,b r e e d i q season, and molt a r e i r d i c a t e d by solid ard broken l i n e s i n the l e f t column. 1971 Dec.
5
Beak clappin3 and c h a s i n ~ n a flock of i
4-6 b i r d s , l a s t i n 5 about 10 minutes,
Flock of 7-10 b i r d s r e s t i n g , preening, a d allopreening in a Eanyan about midday. Some of t h e b i d s i n p a i r s within t h e group. Birds f l y i n g t o and from a feeding a r e a i n p a i r s , joining flock a% the f r u i t i n g t r e e . Flock of 8-10 b i r d s feeding, l a t e afternoon.
1972 Jan. 25
Feb. 3
Feb. 10
Feb.
15
B i r d carrying nesting m a t e r i a l a t Diamolld Head. A t Diamond Head several White-eyes wing f l u t t e r i n g and chasing i n a Kia*xe t r e e .
F i r s t egg of t h e season (estimate, a s n e s t was found during incubation period). Aggression and beak c l a p p i x a t food t r e e s seems more intense. Birds s t i l l feeding i n groups of t h r e e o r four. Bird carrying nesting m a t e r i a l t o a s i t e , but nest w s never completed. a F i r s t fledgling of t h e year. Birds not in flocks of more than t h r e e o r f o u r (family groups )
Feb. 19 Feb. 20 Feb. 21
Feb. 22 March 14 April&Y M y 10 a June 24 July 20
.
Largest number of a c t i v e n e s t s , during t h e 1972 season.
Last complete nest s t a r t e d .
Last incomplete nest s t a r t e d . Last fledqling of the year.
Pi - --r c t
July 25
July 2 9
Sept.
i~melt.
I
Last bird i n molt.
October November Dec. 14
A bird on t e r r i t o r y , s f i g i n q , where it had not been during t h e previous season.
>imerous siqhtinqs of birds in small f l o c k s .
Bird carrying nesting material, but no
nest was started,
I I
1973
Jan. 20 Feb. 18
Bird carrying nesting material, but did not s t a r t nest. Nest started, but never completed. Several b i r d s chasing and beak clapping i n a Fiddlemod t r e e . F i r s t egg of the season.
1 I
I
I
Feb. 26
March 1
March 4
I
Singing extremely common all across campus.
F i r s t fledgling of t h e year. Largest number of a c t i v e n e s t s f o r
Parch 1 1
Kay
15
1973 season.
June 26 J u l y 12 July 20 August 11
Flock of more than 8 birds feeding in a Flonkeypod tree.
Last complete nest s t a r t e d ,
Last egg of t h e season laid.
Last fledqlirq of the year.
-1 6Sound Production Flhite-eyes have a v a r i e t y of vocal sounds. Some species are
capable mimlcs (Chisholm, 1932 ), 4 t h e White-eye i n H a w a i i has been known t o mimic another species (Guest, 1973).
In Japan, t h e
W t e - e y e is a f a v o r i t e cage b i r d , h o r n for its singing a b i l i t y (Mumc,
1960).
Following i s an o u t l i n e of their repertoire,
A. Nonvocal sounds
1. Beak clapping--used
of aggression.
in conjunction w i t h displays; a component
B. Vocal sounds
1. C a l l notes
a. location notes--'tseetm, given when in a flock, o r when
feeding in pairs, by mdle and female.
b. f l e d g l i n g notes-very
similiar t o l o c a t i o n notes, given
by fledglings when hungry.
2. C h i t t e r - a harsh scolding noise u t t e r e d when t h e birds are upset o r disturbed, by both male and female.
3.
Whine--sWiar
t o and sometimes p r e c e d i n g t h e chitter,
given i n conjunction with aggressive displays, k y m l e an3 female.
4. Songs
a whisper song-a .
rambling warble given i n quiescent
periods
t h a t i s so q u i e t i t can not be heard more than about t h r e e meters away; seldom h e a d i n the field.
b, 'flight song'--a
s e r i e s of stretched-out call notes given
when t h e b i r d s take t o t h e air, usually l a s t i n g only a few
seconds.
c
.
primary (terr5t0,r.y) song--a
loud warbling song, given by
-17-
only t h e male.
It i s sung from a prominent position
laithin t h e t e r r i t o r y , and has t h e function of d e f i n i q
the territory.
One s k v i n g bout may include from one t o
50 songs, each song averaging about f i v e seconds and t h e
period between songs, averaging two o r three seconds.
I have heard the primarg song of t h e male i n every month of t h e
year, but t h e r e is a n increase of singing durirq t h e breeding season,
Superimposed on this yearly cycle i s a daily c y c l e c o r r e l a t e d with
nesting cycle (see f i g s 2 a d
the
3).
The d a i l y cycle begins with a period of song about 20 t o 40 minutes i n length a t sunrise. There i s a sharp decrease i n frequency of singing
during the rest of t h e day.
Figure
The s l i g h t increase in t h e evening shown on
3 i s not s i g n i f i c a n t (one-sided t - t e s t ) .
I detelmined these
frequencies from t r a n s e c t walks on f i v e d i f f e r e n t days e a r l y i n t h e
1973 season.
Mees (1.957) reported dawn and evening song i n
Z.
Japanica.
The nesting cycle of individual pairs i s synchronized with a song
cycle such t h a t song increases during the n e s t building, incubation,
and fledgling period and decreases during the nestling period.
The
decrease of singing during t h e n e s t l i n g period mag not be explained bg t h e f a c t t h a t t h e male feeds t h e young and might became very busy carfood and have l e s s time t o sing.
Feeding r a t e increases t o a
during t h e e a r l y fledgling period also.
-
Figure 4 shows t h e individual song cycles in r e l a t i o n t o the nesting
period,
These d a t a were collected f r o m f i v e p a i r s t h a t were each observed
through a t l e a s t one cycle.
One pair nested outside m y o f f i c e and I was
and therefore make
able t o hear t h e i r song fro3 i n s i d e t h e building
almost continous observation on them.
-18A main function of song in t h e HhLte-eye i s t e r r i t o r y defense, and if a male attempts t o s i n g i n a t e r r i t o r y o t h e r than his own, he
i s chased away by both t h e male and female occupying t h e t e r r i t o r y .
Such
an incident i s r e l a t e d i n t h e following account from my field notes.
kLrch 19, 1973--Hest 9-73 i n second day of incubation. from this n e s t i s banded. The female
1245--MAe releived female a t n e s t an3 began t o incubate.
flew i n t o bushes about 1 0 meters from t h e nest. 1306--Male very a l e r t on t h e nest. 1307-Female
Female
feeding in Haole Koa about 12 meters from nest.
h
unbanded b i r d began t o s i n g from a Kukui t r e e about seven meters
from t h e n e s t and w e l l within t h e banded p a i r s t e r r i t o r y . never heard song from this t r e e .
I had
The banded female beam t o c h i t t e r Hale l e f t
loudly, and wing f l i p f r o n t h e area where she was feeding.
n e s t ard flew t o female, and both then f l e w t o H u k u i t r e e and chased t h e intruding bizd. A f o u r t h unbanded b i r d joined t h e group in t h e
Kukui, and f o r t h e next s e v e r a l minutes I could not identFfy any of
t h e individuals involved. Chasing, wing quivering, and wing f l i p p i n g ,
beak clapping, and c h i t t e r i n g ensued.
Two b i r d s flew away and male
approached t h e n e s t and fluffed his f e a t h e r s . 1316--Female joined male i n bushes near nest. of them in t h e foliage. 1326--he of the p a i r approached t h e n e s t anl began t o incubate.
I l o s t s i g h t of both
Another function of song i n White-eyes i s probably t h a t of s o c i a l s t i m u l a t i o n , and ?-rillbe discussed more fully i n t h e s e c t i o n on t e r r i t o r i a l behavior.
incubation period
nest ling period
I
f ledg] ng
perio
nest
building
,
Figure 4. Data are
Singing i n Relation to I n d i v i d u a l Nesting Cycle, f i v e p a i r t h a t wore obsorved through a t l e a s t one cycle (3973). See t e x t f o r f'urther discussion, '
fmln
-21 T e r r i t o r i a l Eehavior
There
Territory i s defined a s any d e f e d e d area (Hinde, 1956).
have been many discussions i n t h e l i t e r a t u r e of t e r r i t o r y function i n b M s (Hhde, 1956; Nice, 191). ?Jot a l l of t h e functions discussed apply
t o IWte-eyes in Hawaii, and t h e m a r e probably s e v e r a l functions t h a t
this behavior does f u l f i l l .
The ! a t e - e y e s
on campus a r e spaced such that each p a i r has an
average of 1.6 acres (range of 45 pairs i s 0.31 a c r e s t o 3.40 a c r e s ; one
a t e r r i t o q measured 6.3 a c r e s b u t it w s abandoned
occurred i n 1973). progresses.
h Parch before breeding
T e r r i t o r y s i z e m y f l u c t u a t e s l i g h t l y a s t h e season a
A t one l o c a t i o n on campus a building w a s being constructed
during t h e beginning of t h e 1973 season and s e v e r a l t r e e s were removed.
A l l of t h e b i r d s seemed t o shift
out of t h e area t o adjacent t e r r i t o r i e s , Another example of very
b u t t h e i r r e l a t i v e positions remained constant,
t e r r i t o r y f l u c t u a t i o n occurred in a group of l a r g e banyans, with a
dense population of singing males (about t h r e e p a i r s per a c r e ) i n 1972
ard
1973. During t h e season of both years, a t l e a s t one pair ( d i f f e r e n t
pairs in 1972 and 1973) moved to adjacent areas t o build a f t e r unsuccessful
nesting attempts. For t h e most part, however, white-eye t e r r i t o r i e s are Figure 5 diagrams t h e t e r r i t o r i e s a s
s t a b l e throughout t h e season. they were in April of 1973.
From one season t o t h e next individual b i d s may s h i f t t o new t e r r i t o r i e s , but usually remain i n t h e same general area.
O f ten pairs
banded on campus i n 1972, f o u r nested on t h e sane t e r r i t o r y , one p a i r
moved t o a new t e r r i t o r y about mile f r o m their 1972 t e r r i t o r y , one
moved t o an adjacent territory, and f o u r p a i r s were not seen, in 1973.
-22The a v a i l a b i l i t y of food has been suggested as being important i n determining t e r r i t o y y s i z e i n some birds. However, White-eyes feed
A t every n e s t
not only on t h e i r own t e r r i t o r g , but on adjacent ones.
observed f o r & q y regular period of time, I obse-med t h e a d u l t s f l y out of t h e t e r r i t o r y a d r e t u r n with food t o feed the young. Other foraging
White-eyes a r e not chased o u t of t h e a r e a , but permitted t o forage throughout.
I have observed foraging ihite-eyes as c l o s e a s two meters
from an a c t i v e %kite-eye n e s t , without being chased (observed a t three d i f f e r e n t nests). Large numbers congregate a t feeding a r e a s (i. e.
, fruiting
t r e e s ) y e a r around, regardless of t e r r i t o r y . Tinbergen
(1957) suggests that food can
be a limiting f a c t o r even
when mutual trespassing i s involved.
Ideally, each t e r r i t o r y would Beer, Frenzel, a& Hanson
support t h e same r e l a t i v e number of birds.
(1956)
f e e l t h a t there a r e a number of f a c t o r s besides food a v a i l a b i l i t y important
i n minimum space requirements f o r nesting passerine birds.
The most
tenable explanation i s t h a t " t e r r i t o r y o f f e r s protection from i n t a r f e m m e
i n t h e orderly sequence of t h e nesting cycle."
I f e e l an important function of t e r r i t o r i a l behavior i n the Itlhiteeye is t h e familiarity of t h e area which t h e bird gains. f o r this, I have observed a b a d e d b i r d gathering nestA s evidence
material on
i t ' s 19'72 t e r r i t o r y , and c a r r y it t o t h e 1973 t e r r i t o r y t o construct t h e
nest.
This p a i r spent a great d e a l of time "tres-passing" and feeding
on i t s 1972 t e r r i t o r y .
The two areas were adjacent.
\
The spacing of birds on campus i s r e l a t e d t o vegetation.
Tjy
r a d ~ i n g l l the t e r r i t o r i e s accodingy t o s i z e , and examininq every a fourth one i n terms of percentage of area covered by vegetation, I found the percent of area covered by veqetation ir.creased as t e r r i t o r y size decreased (see f i g . 6).
Kikka-i (1952) found a higher n&r
of
2 .
-23-
l a t e r a l i s per a c r e i n a wooded area than I found on campus ( t h e comparison may mean l i t t l e as these a r e d i f f e r e n t species). Furthermore,
o t h e r f a c t o r s than vegetation density a r e probably important i n determining t h e f i d d e n s i t y because Ric'nardson and I3owles (l9jll)
reported White-eyes t o be i n reduced numbers i n t h e r a i n f o r e s t s where
t h e vegetation d e n s i t y i s high. Never-the-less, t h i s system of dividing
t h e a r e a in tenns of vegetation density, allows an e f f i c i e n t use of t h e a v a i l a b l e a r e a f o r breeding.
Tompa (1962) found t h a t . in c e r t a i n cases, t e r r i t o z y could Mt
t h e upper bounds of p p u l a t i o n density in Song Sparrows (Xelospiza melodia).
Srown (1964) discussed t e r r i t o r i a l i t y a s a population c o n t r o l in birds
arrl reached t h e conclusion t h a t it probably has n ~ evolved as t h e t major f a c t o r of population c o n t r o l in t h a t even though an e n t i r e population might b e n e f i t , t h e "changes i n gene frequency a r e t h e r e s u l t of competitive advantages accruing t o individual geneotypes r a t h e r than t o t h e group a s a whole."
I f e e l t h a t although t e r r i t o r g
i s s u r e l y r e l a t e d t o t h e population density, t h e r e a r e o t h e r functions
t h a t t h i s behavior I"ulfia-ls in White-eyes. Another function t h a t i s a t t r i b u t e d t o t e r r i t o r i a l behavior is t h a t or" s o c i a l stimulation.
Darling (1952) suggests t h a t "one of t h e
important functions of t e r r i t o r y in breeding b i r d s i s t h e p r w i s i o n of peri~hery-periphery being defined as t h a t kind of edze where t h e r e
i s another bird of t h e same species occupy in^ a t e r r i t o r y ,
.,.
The
breeding t e r r i t o r y has l i t t l e t o do with a sufficiency of feeding pound f o r r a i s i w the brood,
It i s a f o c a l point o r t-do--the n e s t
T e r r i t o r i a l behavior i s That t e r r i t o m i n
s i t e and t h e sin.qirg post--
and periphery."
a social phenomenon, and it has sunrival value."
the Vnite-eye has such a function, I have l i t t l e doubt.
Song ( t e r r i t o r y
defense) was seldom heard from one male without being answered by another. Furthermore, song increased as the birds came i n t o breeding
condition a t the beginning of the season.
That such stimnli can
Lehnnan (l96rc). White-
a f f e c t the behavior of birds has been shown by
eyes
usually sing from prominant positions where they can be seen by
Also, the one pair
adjacent singing males, providing further stimuli. t h a t occupied the l a r g e s t t e r r i t o r y breeding.
(6.3 acres) abandoned it before
ay This suggests that they r a have .preferedW t o be i n an
area of higher density of birds, and more social stimulation.
The two song cycles superimposed on the reporductive cycle may also be explained in terms of increasing the social stimulation.
Durin,~
the f i r s t few minutes of the day the presence of other breedbg males
i s reinforced f o r each pair.
A song hcrease during the f l d g l i n g
period could serve two functions, t h a t of making the parents (male)
more conspicous than the young and in bringing the pair back i n t o cordition t o renest.
A second nest i s built immediately a f t e r the
young become independent, i f not started while they are s t i l l being fed by the adults.
.
RELATIVE SONG POSITION AND APPROXIMATE TERRITORY SI Z E
APRIL 1973
Figure 3.
0.31 acres
6.3 acres
1 . 3 acres
Figure 6. Territow Size i n Relation t o Vegetation. These diagrams represent three t e r r i t o r i e s , ranging i n s i z e from the l a r g e s t on campus t o the smallest. The stifled area represents that area covered by vegetation ( t r e e s , shrubs). The l a r g e s t t e r r i t o r y (6.3 acres) was abadoned before nesting occurred, Measurements were taken i n 1973.
Courtship, Copulation, and Nest S i t e Selection
2 Kunkel (1962) describes pair f o m t i o n i n -, palwbrosa from
avial~g observations.
"During pair f o m ' c i o n the male offers h i s head
t o the female f o r preening, thus suppressing, a t l e a s t partly, her tendemies t o a t t a c k o r t o f l e e . ..,vibrating the wings i s preformed The female a l s o
during p a i r formation and before nest building.
vibrates the wings when s o l i c i t i n g f o r copalation."
I have observed,
i n three w i l d banded pairs, one b i d follouing the other through t h e
n foliage, the bird behind wing quivering, A d in one case the
was following and wing
female
quivering, ard i n one case t h e male; the sex
was not determined f o r the third.
This behavior was not followed by
copulation, and occurred a t the beginning of the nesting cycle, just before nest building i n all three cases. I n i t i a l p a i r formation probably
occurs i n the winter flocks, and the birds remain with t h e i r mate at l e a s t t w o seasons. Copulation has been observed on three seperate occassions.
Ln
one case it occurred about f i v e meters from t h e nest, three days before the first egg.
There was no precopulatorg display.
The male mounted
t h e female six times.
Both then hopped t o a nearby branch and engaged The sequence was s i m i l i a r in the
in allopreening (mutual preening).
other two instances.
Because the birds stay together f o r longer than one season, there
may be no need f o r elaborate courtship t o bring the sexes together.
Pair bond maintanence would be of most importance. Aliopreening i s
very common between mates, and Harrison (1965) suggests t h a t one of the main functions of allopreenirlg i s t o strerqthen t h e pair bond. Kunkel (1962) describes feeding of the female by t h e male in
Z.
palpebrosa,
-28when she threatens him, but I did not observe any feeding between adult birds. Nest s i t e selection was observed a t one nest, but the birds were unbanded so I don't how which was the female o r male. One bird flew
t o a branch i n a Monkeypod tree.
It gave a variation of the 'tseet'
The other bird flew
c a l l note t h a t I have not heard before o r since. t o the spot immediately from an adjacent tree. Nest construction began the same day.
They engaged i n allopreening.
The Nest
Whlte-eyes have "semipendent cuplike" nests (Van Tyne and Bertger, 1971), re,plar in s i z e , shape, and constmction, with the nesting loaterial v a w s l i g h t l y from nest t o nest. the work evenly. 30th sexes build, dividing
The period necessarg f o r completion varies with the
t i n e of season and stage of breeding cycle. f o r each brood.
Nest measurements f o r 1972 and
A neTs nest i s constructed
1973 a r e summarized i n Table
2.
Cup diameter and depth varg s l i g h t l y from nest t o nest, while bottom thickness and r i m thickness deviate more. Nests a r e generally very
re,g.dr
in shape and construction, but I found several t h a t were
One nest had a r i m thickness of 10 mu on one
extremely unusual.
side and 61 mm on the opposite side. irregular shape.
It was verg secure, despite the
Eranches where the nests a r e attached (nests are
usually attached on a t l e a s t two sides and sometinas almost a l l the
way around the cup) I found t o never exceed 13 mu, averaging about
6 .
a d
.
There was no difference i n the nest measurements of 1972
19'73 ( t - t e s t ) .
Table 2
Nest Measurements (in mm)*
CUP
CUP
Diameter Depth Mean
Standard Deviation
Number 56.23 6.30
Iiim Diameter of Bottom Thickness Thickness Branch where Nest is attachad
41.73 7.34 15
18.45 11.80
10
11.62
6.61
18
12
15
*
No significant difference between 1972 ard 1973 measurements ( t - t e s t ) .
Hest material includes a variety of things (grass, f i n e plant material, s t r i n g , t i n f o i l , p l a s t i c , hair, spider web, spider cocoons, leaves, mosses, etc,),
The cup of the nest i s composed of f i n e 5rass
woven together with spider wb. Eragrostis tenella. cocoons;or
The most common type of grass i s
On the outside, colored s t r i n g , plastic, paper,
miscellaneous material is common.
Cocoons a r e reported
in the l i t e r a t u r e f o r other species of Zosterops.
I found the cocoons
used by t h e b i d s t o be f r o m the spider family Arsneidae. I n 1906, Dove stated t h a t Whitewes probably w i p the empty cocoons on the nest a f t e r feeding t h e young: however, I founjl the birds carrying cocoons t o the nest before incubation began, and never saw them being carried t o the nest t o feed the yow.
(I have seenome,
adults feeding fledglings spider cocoons.) Furthermore, many nests had no cocoons, but invariably they had some colored material o r white -paper on the outside.
I feel that the white cocoons and colored
material probably serve t o break the outline of the nest and thereby camouflage it. The nest becomes more d i f f i c u l t t o see giving t h i s
behavior survival value. The nest l i n i n g i s very f i n e material, commonly human hair.
In
two cases, I found the young birds tangled i n this f i n e material, so they were unable t o f l d g e from the nest. the nest. Instead they dangled f r o m
I d i d not find them u n t i l they w e r e dead, so I don't know
the adult behavior. Nest material i s not collected entirely on a birds territory. very common h a b i t i s the stealing of nest material from active nests of other birds, A
I have observed Idhite-eyes s t e a l h g material from
active House Sparrow ( P a s s e r domest i c u s ) and L5nnet (Carpodacus
mexicanus f r o n t d i s ) nests.
Frings (1968) reports t h a t mite-eyes
s t e a l nesting material from the nests of the 'Elepaio ( ~ h a s i e m ~ i s sandKichensis gayi) on Oahu. Location of Nests
One of the most interesting features of nesting i s the nest location
(tables
3 and 3. Height (distance f r o m nest t o ground) ranges from
Distance t o the base
0.6 meters to over 30 meters (mean = 5.89 m).
of t h e tree varies with the type of t r e e but distance f r o m t h e nest t o
the t i p of the branch averages
52.9 c m and i s l e s s variable.
Nests
a r e usually located i n thick terminal cluxnps of vegetation, w e l l protected from the rain and sun, nests also.
The Kind direction i s related t o the location o f
I n t r e e s exposed t o the w i n d (not protected by buildings),
nests were located in the windward side of the tree only 10 out of 77 times. Specialization i n placement of the nest i s not uncommon f o r t r o p i c a l birds.
Ric Wef s (1469) states: "In the tropics, numerous
species construct domed o r pensile nests, choose special l o c a l i t i e s , a s over water, and have evolovednesting relationships w i t h termites and wasps. Thus, nest construction and placement of some species i s
more specialized than i n temperate regions. adult behavior."
The same may be true of
The 'Nhite-ayes seem t o f i t this category.
A hlgh3y variable f a c t o r in nest location i s the type of vegetation
i n which the birds build.
I found nests located i n 42 species of Individual pairs seem t o
t r e e s and shrubs on canpus (see table 3 ) .
show l i t t l e preference for a particular t r e e type, and most pairs built consecutive nests i n different types of trees,
Sowever, one pair b u i l t
a t l e a s t one nest i n 1973 in exact*
t'ne saxe place as one of t h e i r
1972 nests.
f i r t h e m o r e , a _pair in 1W3 b u i l t
out of four n e s t s
on the same branches of two d i f f e r e n t t r e e s , a s a d i f f e r e n t p a i r had i n
1972.
This pints t o the s p e c i a l i z a t i o n of n e s t sites, even within
a vide v a r i e t y of t r e e s .
Table '3
Vegetation i n which Nests were Constructed 1 972-1 973 Common Flame 3aole Koa S c i e n t i f i c Name Leucaena l e u c o c e p h l a Ficus -r e t u s a Citharemlurn spinosum
Banyan
FiddLswood
Monkeypod Wbiscus t r e e
Sananea saman
l'iontezuma sp.
Pithec ellobium dulce
wBamboo Flame t r e e
False Olive Mango
-
Sambusa sp.
3rachychiton a c e r i f olium Elaeoderdron o r i e n t a l e F?n,giferaindica ?!urraya exotica Acacia sp. Casuarina e q u i s e t i f o l i a
Mock Orange
Acacia
Ironwood
Green Ii '
S i l v e r Oak Queen Flower t r e e
Cordyline t e r m i n a l i s
Grevillea robusta lagerstroenia speciosa
Panax
Avacado Strawbemy Guava
Pink Tecorna
Kukui Octopus t r e e Yellow Shower
Tabebuia wntap%la Aleurites moluccana 3rassaia actinophylla Cassia f i s t u l a Cassia javanica
Pink Shower
Pink Shower
Cassia ,grandis
-34Table Common Coconut Palm
3 (cant. )
Scientific H m a e Cocos nucifera Cordia sp.
Cypress Eucalsptus
bwan
Cupressus semper virens Eucalyptus sp. Ficus benghalensis Ficus -religiosa Ficus umbellata Filicium deciptens zybiscus sp. Tpomoea tuberosa Litchi c hinensis Melaleuca leucadendron Psidium gua,java
Brnyan
Baqyan
Fern tree
Hybiscus Xood Rose
Litchi
Paperbark
Guava
Kiawe
Christmas Berry tree African Tulip Tecoma
Pro sopis pallida
Schinus terebinthifolius Spathodea campanulata Tabebuia pallida
Total number of nests Total number of plant species
119
42
Table 3a
Location of Nests iJithin a Tree* Distance from Branch Tip to Edge of Nest (in cm) Distance from Height of Nest Nest t o Base of from Ground (in Tree (in meters) . meters) , 2.11 5.89
Ma en
Deviation
52.9
26.0
Number
29
5
91
*
N significant difference between 1972 and 197'3 measurements (t-test). o
-36Best Construction Nest construction of one n e s t located i n a Fiddlewood t r e e (Citharexylum s~inosum)i s outlined below. the
It :?as t h e second n e s t of
193
season.
The f i r s t brood had fledged 15 days before.
D a y 2--A few b i t s of spider web were a t t h e n e s t s i t e when I
found the nest. The b i r d s v i s i t e d t h e s i t e t h r e e times from The
0750 t o 0910, and both came t o t h e n e s t ~ i t t h e fledglings. h young were fed about t h r e e meters from t h e nest.
O f t h e three
tri-ps, nesting m a t e r i a l was brought only once.'
Day 3--14uch more material a t t h e n e s t s i t e .
During a 30-minute
The o u t l i n e of
observation period t h e n e s t was v i s i t e d 1 2 times. t h e cup s t a r t e d .
Day 5--Hest
s t i l l a t t h e same stage a s on day txo,
The f l e d g l i x g s Seven t r i p s were material.
were fed once in t h e t r e e next t o t h e n e s t t r e e .
made t o t h e n e s t i n 20 minutes, b u t only one with nest-
Day 9--Hest complete with t h e f i r s t egg.
around.
The fledglings noxhere
Adults not making regular t r i p s t o t h e nest. m a t e r i a l well i n t o t h e seven
A t some n e s t s , t h e a d u l t s w i l l c a m nestincubation period.
The time t o complete t h e nest i s usually about
t o t e n days, but a t the beginning of the season I observed a baded
pair carrying material 31 days before completing t h e nest.
Furthermore,
a t t h e beginning of the season and Late i n t h e season, I have fourd n a s t s p a r t l y constructed t h a t were abaidoned f o r no apparent reason (four i n t h e end of 1972 season a i d two a t t h e s t a r t of 1973 season). This phenomenon i s possibly due t o l o x reproductive .drivet', been reported f o r other passerine species ( Y i c k e l l , 1951). An i n t e r e s t i n s behavior was observed a t f i v e d i f f e r e n t nests,
and ;?as
-37Birds would move t h e i r n e s t t o a new s i t e . In a t l e a s t f o u r cases
a t h i s w s a f t e r I had been t o t h e n e s t , suggesting that I may have
disturbed t h e birds.
It occurred during t h e nest building period.
I n these cases, t h e birds removed t h e material, piece by piece,
from t h e old n e s t and reassembled it a t t h e new s i t e . t h e i r n e s t twice before Laying eggs. o t h e r -wsserine species (Flickell, One pair moved
T h i s has been reported f o r
The second n e s t s took no
1951).
less t i n e t o construct, and I could f i n d no s i g n i f i c a n t d i f f e r e n c e
i n t h e distance the second n e s t was l a c a t e d from t ; first n e s t in h!
n e s t s dismantled a s described above, and when nests were completely abandoned during n e s t bullding (see t a b l e 4).
I nade no attempt t o analyze the d i f f s r e n t movements of t h e birds
during n e s t building. K d e l (1962) described t h e technique of Z.
_palpebrosa a s t y p i c a l of b i d s whose n e s t s are suspended between
twigs.
They work from the i n s i d e of t h e n e s t , and while t h e cup i s
beinz fonned they often s i t i n s i d e t h e cup and push with t h e i r breast.
A
first n e s t b u i l t b a 1972 juvenile was one of t h e most 'regular' j
The cup depth, diameter, bottom thickness, and rim thickness
T h i s sugsests
n e s t s found.
xere almost exactly a t t h e mean of the t o t a l population.
t h a t t h e b i r d s need l i t t l e p r a c t i c e t o know which m a t e r i a l t o s e l e c t ,
o r e l s e t h e sate of t h e 1972 juvenile (it w s unhanded) was an a
experienced bird,
I have found no evidence of juveniles building n e s t s
o r helping with t h e i r parents' n e s t s before maturity, b u t they would be zble t o watch, Spacing of :!es.ts
.
m distance between a c t i v e :kite-eye n e s t s averaged 188,16 meters e
(range of 15 meters t o 8 9 meters), Eore regular in s p a c i n ~ was t h e
d i s t a n c e between song positions.
I have obserred two n e s t s a s c l o s e
as 15 meters, but t h e d i s t a n c e botm?n t h e son? p o s i t i o n s was 40 neters.
This averaged 91.9 meters (see t a b l e
5).
I n t e r s p e c i f i c spacing of ?kite-eye n e s t s and o t h e r species n e s t s
may be very small.
I have observedl a c t i v e !Tnite-eye n e s t s 8.1 meters
from a Linnet ( ~ a r p o d a c u smexicanus fr o n t a l i s ) n e s t , an a c t i v e 1 h -
5.7 meters from
(Acridotheres tristis) n e s t , 2.1 n e t e r s from a n a c t i v e
American Cardinal (Cardinalis c a r d i n a l i s ) n e s t , and 1.8 meters f r o m an active House S p a m ~ h s s s r domesticus) nest, ( I n 1972,
I n t e r s p c i f i c defense of t h e n e s t was not observed,
I
The
observed t h e I n t e r u p t i o n of two White-eye n e s t s by House Sparrows.
Sparrows began t o build a n e s t b a Pink Tecona ( ~ a b e b u i apentaphyla) t r e e whem a White-eye n e s t
.th t h r t ~ e young was located.
The male
Eouse S p r r e w pecked the young t o death t ~ m days a f t e r being f i r s t observed in t h e t r e e .
A t a White-eye n e s t i n a Monkeypod
(Szunanea
swan) treeJ a male Sparrow was observed pecking a t t h e n e s t t h e day
before it -as abandoned. The n e s t was i n a c c e s s i b l e so I don't know if
it contained young o r eggs.
In both cases t h e White-eyes offered no
r e s i s t e n c e , and i n t h e former c a s e carded food "L t h e n e s t f o r a f u l l
day a f t e r t h e young were dead.
'
S 9 v d i n t e ~ % c t f x m s - noted s ~ ~ ~ between 'rJhite-eyes and Red-vented
3 l b u l s ( m n o n o t u s jocosus) during the course of t h i s study. Autoqraph (-- a ~ l u s i - t r e e where t h e Bulbuls rosea) lihite-eyes attempted t o chase t h e b i r d s away. were feedi-g,
A t zn
severaP
This w a s observed on t h e Khite-eyes
two d i f f e r e n t days, and i~both cases the B i l b d s iFored and continued t o f2ed,
I obsemed a pair of 2xlblsls successfully chase
0
s s v e r a l Ahite-eyes o u t of a Xonkeypod t r e e 'rih3r-e t h e Bulbuls were c o n s t m e t i n g a n e s t , but they a l s o chased Xynaiahs and Zouss 3parx-oxs away.
Table 4
Distance Bedcusen ~onsecutivelies s of Individual Pairs (-nnmeters
+ken First Nest i s Torn Down; Distance to the Next lbst
Idhen first Nest i s
5
*
Successful; Distance to
Next Nest
When first Eest i s Abandoned; Distance to the Hext >lest .
Mean
Standard
Deviation
?lumber
*
telrt
No significant difference between 1972 and 1973 measurements, for further discussion.
See
Table
5
Distance Between Active White-eye Nests a d Active Song posts ( i n meters) Distance Between
Active White-eye
*
Distance Between Active Song Posts
Nests Mean
188.16
91.94
*
?lo s i @ f i c a n t difference between measurel~entsof 1972 and 19'73.
See
t e x t for further discussion.
Description of Eggs
Eggs belonging t o birds of the genus Zosterops are typically
inanaculate slad vary Tram white t o very ]pale blue (Van Tyne and Serger, 191).
In the l i t e r a
e there are reports of colors ranging f r o m
a
pink-vhite t o blue-green-white
Vincent, 1949).
variation.
(Moreau, 1955; Skead and Ranger, 1%7;
The ~ 0 3 . 0difference has b a n attributed t o individual ~
H
er, I discovered t h a t them i s a color change with
becoxe more opaque
appears t o beesme
;ably due t o t h e dwelop-En~5 embrgo), the color
seems b k k h .
I the nests -re not checked f
several tjmes during incubatfon, and several were found a t d i f f e r e n t
stages of P
appeal. t h a t the color variation was great
within the s
~jl 1908,
k g
the eggs of
3.
japnica
as
hiw
0.65 x
0 5 inches (16.5 x i .
found f o r the s
ii.
i s WE Within the r w e of what I
The mean size of 35 eggs from 1972
a~3. 1973 i s 16,s x 1
re was no significant difference between
the egg measurements of the t w o seasons ( t - t e s t ; see table 6 ) .
The m a n clutch s i z e fay t h e t w o seasons
is
31 .4
eggs,
I f o d
several nests. d t h t
was fouml by
one nest of
%ve eggs near Pakapu P o i n t
os four eggs,
W.Y. Bmmm in 1972.
AU other nests held t h m e
There was no significant difference betmsn t h e t ~ . o seasons (t-test;).
Table 6
Egg Measurements
Width
*
(in m )
Length (in mm)
Weight Clutch (in grams) Size
Deviation
Number
0. 52
06 .8
0.13
35
35
20
25
*
No significant differences in measurements of 1972 a d 19730
Laying, Pipping, a d Fltching I n 1952, Skutch reported t h a t t h e time of laying, f o r a p a r t i c u l a r
l o c a l i t y and species of b i r d , i s usually stamlard with l i t t l e variation. The hatching time i s sonewhat more variable, but usually occurs more o f t e n i n one q u a r t e r of a 24-hour day. Mhite-eyes, This seems t o be t h e case f o r
Nine eggs in f i v e nests were laid b t w e e n sunset a n l t h e For exact times see Table 7.
A t one nest
morning of t h e following day.
t h e last egg of a t h r e e egg c l u t c h was l a i d between 0633 a d 0645.
I
have no evidence of arly egg being laid l a t e r i n the'day, a d i n l i g h t
of Skutch's =per,
I f e e l laying t i m e i s e a r l y morning.
~t probably i s not
during t h e night, since t h e female does not s i t on t h e n e s t a t night
u n t i l a f t e r t h e t h i d egg (usually t h e last egg) i s l a i d , Hatching usually i s e i t h e r a t night o r e a r l y i n t h e morning. checked seven n e s t s t h e evening before hatchirg and again the next morning, a d determined t h e followkg,
I
In f o u r n e s t s eggs were not
hatched before 1860, 1700, 1800, and 1700, and not a f t e r 0715, 0635,
0900, and 0830 t h e next morning,
was p a r t of a t h r e e egg clutch.
Only one hatched during the day. Two hatched between 1700 a d 0635,
It
a d t h e t h i r d between 0635 a x 1900. rl
Signs of pipping may appear a s long as 24 hours before hatching, as small cracks a t t h e l a r g e end of t h e egg, near t h e long diameter of t h e a i r sac (see fig. 2). before hatching.
A s a r u l e a l l eggs are pipped t h e even*
Ageing of the Eggs
Several techniques have been developed f o r determining t h e age
of eggs ( L e e , measurinq t h e wei&t l o s s during incubation, c a d l i n g
t o determine embryo s i z e : Westerskov, 1950).
However, t h e eggs of
4 Vhite=eyes are so small, t h a t with the s c a l e s I was using, I could not
determine weight l o s s accurately enough t o age them.
Candling would
probably be useful, as t h e s h e l l s a r e transparent enough t o see through with l i t t l e l i g h t . The e a s i e s t method I d i s c w e r e d w s measuring a the
s i z e of t h e a i r c e l l a t t h e l a r g e end of the e g g , Westerskov (1950) discussed t h e use of t h i s technique i n pheasant eggs.
During incubation, t h e evaporation of water from t h e egg a d
t h e shrinkage a d s o l i d i f i c a t i o n of t h e egg contents i n t o a chick cause
a gradual growth of t h e a i r c e l l .
In t h e White-eye 'egg t h i s c e l l i s
e a s i l y v i s i b l e through t h e shell of t h e egg, and t h e diameter i s e a s i l y measured. The age can be determined to within two o r three days, and The
t h e r e l a t i v e age of the eggs within a clutch is e a s i l y found.
o l d e s t egg ( l a i d f i r s t ) has t h e l a r g e s t c i r c l e , and t h e last has t h e
smallest.
In f i v e n e s t s , I forrnd only one egg t o be an exception.
The c i r c l e was n o t r o d , and it w a s d i f f i c u l t t o determine what s i z e the
diameter was.
The c i r c l e size increases fPL eggs that do not hatch also.
I have diagrammed t h e a i r cell diameter on d i f f e r e n t days of incubation
in Figure 7.
border lines f 2 SO center connects mea ns nurn bers indicate sample size
days of age
Figura 7.
A i r Cell Diameter i n Relation t o Age of Eggs.
-46Incubation Period Incubation period i s defined a s the time which, with regular incubation of a newly l a i d egg, elapses u n t i l the yoegg. has l e f t the
A practical d e f i n i t i o n i s the time from the laying of the last
egg t o the hatching of the Last egg vhen ell t h e eggs hatch (Nice,
1953)
This subject has been the su3ject of much discussion i n the l i t e r a t u r e
concerning Zosterops.
In 1953, Nice wrote, "Zosterops, the Vhite-eye o r
S i l v e r e y e , has attained world-wide fame f o r t h e shortest period of any bird--9 t o 10 days.
This rumor started i n a c'areless observation
In eleven o r more nests t h a t have been the incubation period lasted 11 t o
i n Nw Zealand i n the 1880's. e
carefully watched from 1870 t o 1*3
-
=days
.
"
-
I n t h i s study I measured the incubation period a t four nests, i n
which a l l the eggs hatched.
The r e s u l t s are presented i n Table 7.
Assuming hatching occurs i n the morning, the incubation period i s 11 days i n aU. four cases. However, if hatching occurs a t night, it could
be as short as 10 days and 1 0 hours. occurs i n the morning. Nestling Teriod
I f e e l that hatching probably
"A young bird i s a nestlinq from the time i t hatches u n t i l it leaves
the nest" (3erger, 1961).
In the Literature Zosterops i s said t o have
a nestling period varying from 9 t o 13 days (%ridson, 1952; Gilliard, 1967; 'dilkinson, 1931). I found it t o be between 9 and 10 days a t six nests
If t h e nest i s
t h a t were not disturbed fxon day eight t o fled@ng.
disturbed (i.. e a day early.
, by d a i l y
weighine; of the yow),
the chicks nay leave
-47Table 7 Incubation and Nestling Periods
Laying "est > , h b e r of & Year Eggs
Segin Iiatching Incubation of (morning ) Chicks
Fledging Incubation ??estling from Period Period &st
10 days, 10 days,
None a t f%y15,1800; ?Iay 26, 1435 by 1ilayl6, w15*
17 hours, 13 hours, + 6 hours 2 6 hours
ll* days,
masdmum
mY b
May 8,1.730*
---Hay 21, 1100
---9 days 9
U b g b y 12
---------10 days, 18 hours, - 8 hours +
+ 4 hours 9 days, 13 hours,
2 hours,
M r i ,1630; Par.31, a2
one by Mar. 1430 22,1100; one no hatch. m y b June12, 1214* June 22, 1 007+
Wby
+ - 10 hours
9 days, 12 hours, + - 1 0 hours
m y b Apr7,1230; One on Apr8,09OO*
Apr.8
Nons a t Apr18,1800; m y b A~19,0900*
----
---9days,
m y b Mar17,llOO;
OneW8,
Marl8,
0@+5
between
0633 & 0645
%by Nar29,0635; Apr. 7, One by 1200* Mar29,19OO
None a t Apr. 22, Apr12,1700: 1000 3 sS. Apr.13, 0830; one no hatch
6 hours, 2 7 hours 2 6 hours
11 days,
----
9 days, 9 hours, + - 8 hours
*
t h i s time represents t h e first o r Last time a nest was checked on a particular day, therefore it i s a minimum o r maximum time.
48Nest Attentiveness Nest a t t e n t i v e n e s s i s defined a s t h e a c t u a l time spent a t t h e n e s t by e i t h e r o r both members of a p a i r and t h e p e r i o d i c i t y of such time (Baldwin and Kendsigh, 1927). I n t h e !4hite-eye both sexes a r e
reported t o incubate and feed t h e young (Van Tyne and Berger, 1971),
and I could f i d no difference i n the behavior of male and female a t t h e nest.
each other. There i s no ceremony a t t h e n e s t when t h e b i r d s r e l i e v e
I detenained constancy on t h e b a s i s of t h e formula siven by Skutch
(1962) where T = 100
s : and
T = p e ~ e n t constancy. S = t o t a l time i n
sessions a t the n e s t , and R = t o t a l time in recesses from t h e nest.
I modified t h e equation s l i g h t l y by taking t h e t o t a l time t h e bird w a s
a t o r away f r o m t h e n e s t during an observation period, r a t h e r than
& only using complete recess a session time.
Furthermore, I determined
percent a t t e n t i v e n e s s f o r each n e s t observed, and averaged these percentages t o determine t h e mean constancy f o r any one dqy of incubation and n e s t l i n g period,
In this w y no one n e s t contributed more than another, a
even though it may have been observed f o r a longer period of time. It
i s this f i n a l mean t h a t i s plotted in Figure 8.
S t a r t of incubation i s noted by an increase of n e s t attendance (from
40% t o near 100s) and then t h e r e i s a s l i g h t drop on t h e second and
t h i r d day, Skutch (1962) s t a t e s t h a t i n passerines constancy i s often
l e s s a t t h e beginning of incubation, e s p e c i a l l y i n the t r o p i c s , and gives t h e example of a N s h t i t with 43,5$ constaricy on t h e fourth day of incubation. This might explain the drop i n n e s t attendance on the
second and thin5 day, but t h e nurnber of n e s t s observed i s srrall, s o caution must be used i n i n t e r p r e t a t i o n ,
-49The o v e r a l l attendance remains h i & during incubation, even with t h e above mentioned drop on tine second and t h i d day.
It i s above
70% f o r all days, and above 805 f o r a l l but t h e second and t h i r d day.
Constancy decreases from t h e day of hatching u n t i l it reaches O$ on t h e ninth day. Incubation a t night continues u n t i l t h e eighth night.
Related t o t h e n e s t attendance i s t h e length of sit tin,^ bouts (fig. 9).
In determining t h e mean lengths on various days, again I
allowed no one n e s t observation t o contribute more than another t o
t h e final mean.
During t h e incubation period t h e 'siuts ranged from
9.5 t o 40 minutes.
Skutch (1962) r e p o r t s several f a c t o r s t h a t m y a f f e c t t h e length a
of a s i t t i n g period: species e a t s ; weather.
a c t i v i t i e s of t h e mate nearby; type of food a
I have observed s i t t b q 3hite-eyes leave t h e
The Ir%ite-eyes e a t a
n e s t t o join t h e i r mates, feed and/or preen.
v a r i e t y of f r u i t and i n s e c t s , but I have observed no courtship feeding
(reported f o r Z, palmbrosa; Kunkel, 1962).
t h e length of s i t t i n g bouts f o r t h e species.
Food may help determine Also length of t h e This i s
a t t e n t i v e periods decreases during the n e s t l i n g period. undoubtedly related t o t h e increased r a t e of feeding.
A s more t r i p s
are required t o bring food a s t h e chicks grow, t h e s i t t i n g bouts must
decrease i n length. Adverse weather and r a i n increase t h e constancy of incubation,
I observed this phenomenon a t one nest, i n e a r l y 1973. There was very
bad weather throughout t h e incubation a d n e s t l i n g period.
I did not
f i n d the n e s t u n t i l t h e f i f t h day of incubation, but constancy f o r t h e
followinp days was: Day
5,
90.g; D y 6, a
loo$;
Dy a
7, 1004; %y
8, 1005;
Day 9,
loo$;
D y 10, a
9 ; ; Day 11, 100.$. These f i g u r e s a l l represent a t 7:
On day 9 I
l e a s t one hour observation w i t h t h e exception of day 9.
-50observed t h e n e s t f o r only 40 minutes,
During t h e n e s t l i n g period
Cn day 7 t h e
t h e atterdence remained much higher than normal.
constancy was 1005 (43 minutes of observakion) and on day 8 i t
973 (46 minutes observation).
G n day
9, when I have never observed
a brooding a t any o t h e r n e s t , t h e percent constancy w s 94% (30 minutes
observation). Because of t h e high rate of attendence, t h e r a t e of
feeding was f a r below nonnal, and the chick l o s t weight on the t h i r d
day and never reached 'normal"
(-- 2 standard deviations below t h e mean).
The
Brooding continued t o day 13 when t h e parents abanddned the nest.
chick died i n t h e n e s t on day 14. The n e s t was i n a verg expased p h c e , and t h e w i n d very strong,
It rained every day, f o r a t l e a s t a portion of t h e day.
original& two eggs,
There were
two hatched, b u t one chick was gone from the There were several
this
n e s t on t h e second day of t h e n e s t l i n s period.
n e s t s of d i f f e r e n t pairs t h a t b u i l t i n l e s s exposed places during session of bad weather
that were completely successful,
start incubation
hatch
fledge
JI
J.
4
numbers indicate number of nests observed
Days
Figure 8.
Percent of Time the Nest is Attended.
start incubation
J.
hatch
C
numbers indicate number of nests observed
Days
Figure 9 .
Length of Sitting Bouts in ,%lation to Nesting Cycle.
-53Feeding of Zestlings Both parents c a r q food t o t h e y o u q .
The y o q gape when the
parents a l i g h t o r land on the n e s t rim, apparently i n response t o t h e mechanical. movement of t h e nesfjas they gape r e a d i l y i f the nest
i s tapped gently.
of t h e nest-s,
The parents then place t h e food deep i n the t h r o a t and the young swallow,
In t h e l a t t e r p a r t of t h e
nestling period t h e young become vocal as t h e parents approach the
nest. feedA t fledgirg they
begin t o wing quiver while begging.
I observed
in d e t a i l a t 10
- 15 n e s t s ,
and measured f e b i n g r a t e s a t t h r e e
nests.
Nestling food not analyzed i n detail; however, a t one nest I was
a b l e t o observe from a close distance a d i d e n t i f y some of the food given t o t h e young:
Day 1, two inch worms ( ~ e ~ i d o p t e r a txo flying ),
L ~ s e c t s ;Day 2, a grasshopper; Day 6, two f i g s from a Banyan (Ficus sp.) t r e e , a Nock Orange (Xurraya exotica) f r u i t , f r u i t from an Octopus (Crassaia a c t i n o p b j l l a ) t r e e , These data suggest t h a t there are more
i n s e c t s fed e a r l y i n the nesting cycle, but there i s not enough evidence t o make a strong statement. Davidson (1952) found a simlliar s i t u a t i o n
in that i n s e c t s and green c a t e p i l l a r s f a d most of the d i e t of
:bite-eyes u n t i l t h e day before fledging when r a s b e r r i e s were fed.
The feeding r a t e increases f r o m a p p r a x h a t e l y one o r two feedinqs
per hour on t h e f i r s t and second day a f t e r hatching t o a s
mw a
a s 14
f e e c i i n ~ sper hour two days a f t e r fledging, plotted 7Ln Figure
Data f o r three nests a r e
1 0 , and t h e regression l i n e (slope =0,177).
The p r o q r e s ~ ~ ~ e increase i n feedin? r a t e i s urxierstarsiable i n that
when t h e c3icks a r e newly hatched, the "chief need is not food but
warmth" (van 1 p r and Berger, 1971). 7.; -
Food becomes more i m p o r t a ~ t2 s
-9t h e b i r d s mature. Furthermore, Ricklefs (1968) points out t h a t t h e food processing organs m y not be a s e f f i c i e n t i n a newly hatched
bird as l a t e r .
Figlure 10 shows t h e feedings/ hour/youq, but t h e r a t e a t which food i s brought t o t h e n e s t by t h e a d u l t s v a r i e s with t h e nunber of young i n t h e n e s t , t o a c e r t a i n extent.
This phenomenon has been shown
A t one
nest,
t o be t r u e for o t h e r species of passerines ( ~ k u t c h ,lq4.9).
two young were l o s t (probably eaten by a l i z a r d ; see page 67 ) and the
parents w e r e l e f t feeding o n l y one chick instead of three. The r a t e a t
which t h e a d u l t s brought food decreased f m what is nontal a t a n e s t with three young, on t h e second day a f t e r loosing t h e young. However,
on t h e f i r s t day that t h e young were l o s t , t h e parents brought food f o u r times i n one hour and t h e chick accepted it only three times. the entire s i t t i n g For
u t , the a d u l t held t h e food in i t s b i l l , and flew
O t h e t h i r d day, food w a s refused n
with it a t t h e end of t h e bout.
twice i n a h a l f hour period by t h e chick and a g a b t h e parent
held the
it in t h e bill.
This was not observed on
consequent days, a d
r a t e of carrying food was equal t o what t h e chick accepted, W i n g e r (1967,1970) desclrib ed 'rJhite-eyes a s f eedinq helpers (any b i r d which assists i n t h e feeding of another individual other than i t s mate o r offspring; Skutch, 1961). H reported immature and a d u l t b i r d s e
feeding other n e s t l h g s (i4hkte-eyes, Linnets, and House Sparrows) in h i s aviarg.
I found t h a t i n 1972 t h e b i r d s i n
aviary r e a d i l y fed
several f l e d g l i n g s introduced t o t h e cage, b u t i n 1973 the same b i r d s iqnored a rh'hite-eye fledgling introduced t o t h e cage. S e v s ~ a years l
ago I had a fledgling i n a cage i n q y apartment, and about seven o r e i g h t wild b i r d s carried food t o the window, b u t would n o t e n t e r the house t o feed the etlb-k.
3 1973, 2. %die % i t h (personal comunication) 1
-55told me of a White-eye feeding a l i n n e t n e s t l i n q at a l i n n e t n e s t a t
Barnand Head.
I have not observed 'dhite-eyes feeding young o t h e r than
their own i n t h e wild.
I feel t h i s i s not a co.mon behavior in t h e
o r i n unnatural conditions such as an
w i l d , occaring infrequently
aviary.
Days
fledge
Figure 10, Feeding Rate of Young in Eiehtion t o Age of Young. Three d i f f e r e n t n e s t s were observed (represented by d i f f e r e n t symbols on graph), and each symbol represents a t l e a s t one hour observation. The regression l i n e i s plotted with a s l ~ p e of 0.177.
-57Developent and Growth
The White-eye i s a l t r i c i a l , hatchin5 naked (except f o r two small tufts of down over t h e eyes) and helpless.
Chicks open t h e i r eyes on They e x h i b i t
the f i f t h day a f t e r hatching, a d make vocalizations.
a fear response (crouching i n t h e n e s t ) and begin t o preen on t h e
e i g h t h day, and w i l l leave t h e n e s t i f disturbed on t h e ninth day. The e a r l i e s t I have observed b i r d s peck a t food on t h e i r own and b i l l
wipe i s f o u r days after fledging (based on observations of f o u r h a d
raised birds).
I a l s o observed t h e f i r s t successful head s c r a t c h on
t h e seventh day a f t e r fledging, t h e first c h i t t e r i n g on t h e eighth
d a y , and t h e f i r s t water bath on t h e 12th day a f t e r fledging.
During t h e n e s t l i n g period t h e r e i s a gmdual change i n t h e
r e l a t i v e abount of time spent in various a c t i v i t i e s . Based on observations
of one n e s t and one hand raised b i r d I compiled t h e d a t a shown i n
i
11.
O t h e f i r s t day t h e b i r d s do l i t t l e except r a i s e t h e i r n
heads and gape.
O day six, even though t h e eyes a r e open, n
Sy day 10
*#J
of dter
t h e time i s spent sleeping.
a v a r i e t y of other a c t i v i t i e s
are common.
They s i t and look out of t h e nest, p e n themselves,
ard begin t o move about, but 4-6s of t o t a l time i s s t i l l spent sleep in,^.
Feather t r a c t s can be seen deep in t h e skin by t h e second day
hatching, and most are open by t h e t e n t h day.
Not all the t r a c t s
appear a t t h e same time, and generally s p e a k h z , those that appear
f i r s t are the f i r s t t o unsheathe
The head i s the last part of th9 body t o fledge
This has
t o become feathered, and i t i s not uncommon f o r t h e chicks x i t h the head partially bald and/ o r s t i l l i n pin feathers. been noted as common among
other species of Z o s t e r o ~ s' Yoreau (1957). q
The general daily development is outlined below.
This is based
on observations of s i x chicks a t two nests.
Day 1--Chicks naked except f o r two t u f t s of gray n a t a l down above
t h e eyes; eyes closed.
Day 2--Feather t r a c t s a r e v i s i b l e deep in the skin; spinal, femoral,
ventral, humeral, and wing feathers easi7y seen but t h e t r a c t above o i l gland much deeper; head completely naked erclcept f o r down. D a y 3-All t r a c t s v i s i b l e , and the primaries, secondaries, and
v e n t r a l t r a c t s just beginning t o push out of t h e skin.
Day &--The f i r s t row of w i n g c w e r t s (upper) o k of t h e skin, and
head t r a c t s v i s i b l e deep under the skin.
Day 5--Primaries are about 6-8 mm i n length; eyes barely open. Day 6--Fenoral t r a c t beginning t o open; all v e n t r a l t r a c t s opening,
Day 7--Head feathers and scattered feathers on the outer part of
the l e g a r e s t i l l under t h e skb; neck, auricular, t a i l feathers, a n a l c i r c l e t , submalar t r a c t s s t i l l pins; spinal, humeral, primaries, secoradaries beginning t o open. D y 8-Feathers a on back open enough t o give an overall green color begging vocalizations
t o the chicks; f e a r response i n some young;
common. Day +-Head t r a c t s stiU. not open, but
other t r a c t s open;
will
I
leave the nest when d i s
.
Day 10--Head t r a c t be,ainnirq t o open; fledge; location c a l l note,
1
h y 23-3e-ring
complete.
Day 30--Independent and indistinguishable f r o m the adults.
awakequiet
DAY 1
DAY 6
ACTIVITY
DAY 10
OF NESTLINGS
Figure 11. Esch diagram represents one hour observation of one chick or one nest. Day 1 and 6 were observed at the nest, day 10 in the laboratolly.
-60To measure the gmrth of chicks, d a i l y weights were taken a t several nests. About one gram per day i s gained t o the seventh day, ofie more gram giving 8.28 (average)
and f r o m day seven t o ten (fledging) grams t o t d l weight, ( ~ i c k l es , 1968). f
7
The pattern i s typical f o r a small a l t r i c i a l bird
In Figure 12 I have graphed the growth curve,
periods a r e not uncommon
Rapid growth r a t e s and short nest-
in s
d passerine birds.
Lack (1968) suggests that growth r a t e s are
"ecological adaptations f o r breeding" and since gronth requires energy, the r a t e of grarth depends on how many young can be .fed by the parents.
A s mentioned e a r l i e r , feeding r a t e of ?.lhite-eyes increases t o a very
high point (about 10 feedings/hour a t fledging).
However, the weight
gain a t this paint i s leveled off.
Whether o r not there i s a d i r e c t
relationship between the number of young t h a t can be fed and the growth
q r a t e i n White-eyes ,I can not say from xy data.
3icklefs
(1973) f e e l s
t h a t energy requirements of the young are not balanced against broad
s i z e , based on a review of many b i d species;
rather growth r a t e i s
related t o the precocity of develoysaent (those t h a t develop l a t e have
rapid growth).
Yhite-eyes develope l a t e (i.e.,
can't f l y when leave
the nest) and have rapid gronth ;rates.
decrease in weight a t fledging.
There appears t o be a s l i g h t
This i s comon in mw passerine birds a
due t o a l o s s of water ( ~ c k k e f s ,1968).
However, this decrease i s
not significant i n White-eyes (one-sided t - t e s t )
.
The nestling Period i s about ten days (see page 4 6 ) , and during t'nat time the chick doubles i t s m i g h t three times.
A t fledging the
youny a r e not able t o f l y well, but within three o r four days a f t e r lea* the nest, are able t o f l y f o r short distances,
A t one nest
I measured the distance a chick was able t o fly on several successive
days.
On the day of fledging the chick fluttered from the nest t o
the
-61
ltro days later it flew
ground, covering a distance of two meters.
seven meters and did not loose a l t i t u d e (the wings m r e wit hi^ the
range of a d u l t s i z e ) .
tlowe~er, a t another n e s t one younz flew over
15 meters and gained a heizht of about four meters on the day of
fledging, so there i s some individual v a r i a t i o n , but t h e ability t o
f l y t h i s well a t fledging i s verg unusual.
border lines? 2 SD center connects means numbers jndicate sample stze
Figure 12. Gmwth-weight Curve in Relation to Age of Chicks. The data are from 1972 and 1973. There was no s i g n i f i c a n t difference i n data from the t w o seasons.
liest Sanitation Xest s a n i t a t i o n i s complete. Generally speaking, f o r t h e f i r s t
few days a f t e r hatchinq t h e f e c a l sacs(well formed, enclosed i n a gelatinous membrane f o r e n t i r e n e s t l i n g period) a r e eaten, and toward t h e end of t h e n e s t l i n g period they are c a r r i e d away by t h e parents.
I have observed a f e c a l sac c a r r i e d as e a r l y a s t h e t h i n 3 day a f t e r
hatching, and eaten as l a t e as t h e ninth day a f t e r hatchinq.
A t one
n e s t a chick defecated over t h e s i d e of t h e n e s t without t h e parent r e t r i e v i n g the f e c a l sac on t h e day of fledging. carthe f e c a l
s a c s o r eating then, t h e r e i s no accumulation on t h e ground t o r e v e a l t h e presence of a n e s t ,
Egg s h e l l s a r e probably carried away a f t e r hatching, but I have not
observed t h i s . 1 have found s h e l l about t e n f e e t f r o m a n e s t on t h e
mornirq of hatching when there was no wind.
n e s t i s removed by t h e parents. unless tney are broken,
Foreign material i n t h e
Unhatched eggs remain i n t h e n e s t ,
For example, in t h e case of one f o u r egg c l u t c h ,
i n which an unhatched egq was broken, t h e broken egg disappeared on
t h e second day a f t e r t h e hatching of t h e o t h e r three.
The feldgling period i s defined a s t h a t time f r o m t h e leaving of t h e n e s t t o complete independence of t h e young (Berger, 1961). cases, this period was between 15 and 23 days.
In f i v e
It was exactly 20 days
O one occassion n
f o r one brood and between 19 and 21 days f o r another.
I o3served the parents chase t h e youn,? from t h e i r t e r r i t o r y , arid new
n e s t , on the 26th day a f t e r fled$ing.
Adults beg-in nest construction
about one week before t h e young of t h e previous brood are i n d e p d e n t .
D
These findings a r e similiar t o those reported i n the l i t e r a t u r e f o r
-64t h e germs Zosterops.
I observed a c t u a l fledging a t only one nest.
The young stretched
and looked out of t h e n e s t , periodically during t h e morning, sleeping
between a c t i v e periods. A t 1430 one of them was about seven centimeters The two b i r d s i n
from t h e n e s t , on t h e branch supporting t h e nest. t h e n e s t hopped on t h e n e s t rim.
I.Jhen t h e a d u l t s approached Kith
food, a l l three young begged and hopped up t h e branch toward t h e parents.
They did not return t o t h e nest.
A t fledging, t h e parents become m o r e vocal.
For t h e f i r s t couple
of days c h i t t e r i n g i s verg common, and singing iracreases (see f i g . 4).
The young can not y e t fly, and thus a r e r a t h e r vulnerable.
I they f
f l u t t e r t o t h e ground, both parents swoop and reach t h e ground with t h e chick. However, t h e a d u l t s f l y past t h e young alld invariably an
observer watches t h e a d u l t s fly up from t h e ground, loosing t r a c k of t h e chick. This diversiona.ry t a c t i c i s so predictable
I o f t e n used
it t o c a t c h t h e a d u l t s a t t h e nest.
I dropped t h e young i n f r o n t of
t h e n e t , causing t h e a d u l t s t o swoop down and past t h e young b i r d , i n t o t h e mist net. Another diversionary t a c t i c tkt I observed a t one n e s t concerned :
a Large dog t h a t was in t h e a r e a a t t h e time of fledging of t h e young.
Both a d u l t b i r d s flew about one meter above t h e ground and j u s t ahead of t h e dog, and 1
it away fmm t h e young, After about 100 meters, t h e
Along these
parents f l e w high i n t h e air and returned t o t h e i r young. same l i n e s is behavior
which served t o d i s t r e c t m e when I observed a
n e s t from too c l o s e a distance.
One b i r d f l i e s d i r e c t l y toward m e
or
lox t o t h e g m d conspicously, while t h e other slips t o t h e
nest.
I
have seldom seen t h e bird going t o the n e s t , even though I a aware of n
what is hagpenins.
It always takes m by suprise. e
-65After fledging, t h e young remain in t h e n e s t area. They cannot
fly but hop and c l i n g t o branches,
t'ne f l o o r of
Gne newly xiedged chick w s placed on a
a v i a r y twice, and both times h e d i a t e l y hopped t o the
n e a r e s t branch and then hopped up t h e f o l i a g e u n t i l reaching t h e highest point i n t h e cage,
A t one n e s t I f o n d t h e yow
(two chicks) about
t e n meters from t h e n e s t on t h e day a f t e r fledging, and 15 meters from t h e nest t h r e e days a f t e r fledging, chicks can fly and move well enough
It i s about one week before t h e
to follow t h e parents.
They then
move throughout the t e r r i t o r y and general area as a s f a m i l y group, sometimes joining o t h e r family groups t o form small f l o c k s of slx o r seven birds. The parents feed the young u n t i l they become independent.
This p a t t e r n has been t r u e of every n e s t I have observed. When t h e young become indepenlent, they may remain together f o r a t least a s h o r t period,
I have f e w observations of juveniles once they
leave t h e i r parents, but two chicks were found roosting together two days
a f t e r becoming e p n d e n t , near t h e n e s t t r e e (10 meters). Another
juvenile was seen i n a feeding flock of about 25 b i r d s , 72 days a f t e r fledging (50 bays after becoming M e p e n d e n t ) about one-half mile from where it had fledged.
%
T o 19'72 juveniles w e r e found breeding i n w
1973,
both within one-quaxpte~ m i l e from where they fledged.
*
3reeding Success
e
Adult mortality on campus may be f a i r l y Pow. on campus, t h a t
Of 28 b i d s banded
a t e r r i t o r y on campus, 18 (67$) were l m t o be a
N 'search' was made f o r these birds o Sightings of juveniles were of
alive at l e a s t f o u r months later,
s o the percentage may be hiyher than indicated.
were fewer,
Of 23 f2edglin.r;~ banded a t t h e n e s t i n 1972, only two
found breeding i n 1973.
Ykcther this indicates t h z t they move o u t
the area o r die, I d o n ' t -bow,
-65I deterarined nesting success on t h e b a s i s of percentage of egqs
ard young i n i n d i v i d u a l n e s t s , r a t h e r than t o t a l eT27;s o r young.
The
percentages of succoss f o r each n e s t were then averaqed t o determine t h e o v e r a l l success of t h e p o p l a t i o n .
9y doing t h i s , l a r g e clutches
do not contribute more t o t h e success o r f a i l u r e f i g u r e s than do small clutches.
I found no d i f f e r e n c e i n success r e l a t e d t o c l u t c h s i z e ,
so I f e e l t h a t t h i s i s important.
O f the eggs that were l a i d ,
83.5% hatched over two seasons (based
6 n e s t s ~ f o r1973).
Eighty-
on 18 n e s t s , 56 eggs f o r 197'2 a d 17 eggs,
two percent of t h e chicks t h a t hatched, fledged (48 young, 19 nests i n 1972: 16 young, 7 n e s t s in 1973). and 58.6% of eggs l a i d , fledged (21 nests,
59
eggs i n 1972; l& e s t s , n
33 eggs
5-n 1 9 3 ) .
There were no
s i g n i f i c a n t d i f f e r e n c e s i n t h e two seasons ( t - t e s t ) . Mice (1957) found t h a t open nesting, a l t r i c i a l b i r d s i n t h e IJorth Temperate Zone average 4% success. FWthemore, Ricklefs (1969) s t a t e s
t h a t "In general, b i r d s of humid t r o p i c a l regions a r e l e s s successful breeders than ternpepate species." This means t h a t t h e nesting success Each pair ( p o t e n t i a l average of
of t h e White-eye (58.645) i s very high.
t h r e e broods) would contr5bute 5.52 young t o the population in a season.
O f t h e f a c t o r s a f f e c t i n g t h e nest*
mortality, weather w s t h e a
wind o r storms,
most important.
S i x out of
33 n e s t s f a i l e d due t o t h e
Poor n e s t construction and interference by animals other than man each contributed t o t h e lowered success of t h r e e nests. In five nests, an
egg o r chick disapmared d u r i n s the cycle, and I don' t have d a t a on t h e cause. Fifteen of t h e 33 n e s t s were 10@$ scccessful.
Predation was obsemed i n only o m instance.
2. m d i e S n i t h t o l d
m of a newly fledged Xhite-eye t h a t was r e s t i n ? i n Yaole Koa, about two e
-67f e e t from the ground.
An a l b i n o mon;l;oose xas seen running fron t h e
s t a n d of vegetation with t h e chick.
The parents c h i t t e r e d , but t o no
avail.
I suspect predation i n one case.
A t one n e s t t'm chicks disappeared
f r o n t h e n e s t on t h e same day J observed a l a r g e l i z a r d (Anolis) within about one meter of t h e n e s t and on the same branch.
I had been obsemdng
t h e n e s t d a i l y , and had not seen t h e l i z a r d present before o r aI"ter t h e disappearnace of t h e young. reptile.
I t h h k they were probably eaten by t h e
that
The young weighed o n b t h r e e grams, w e l l within t h e s i z e
t h e l i z a r d could have e a s i l y eaten.
Xikkawa (1962) r e p o r t s that domestic
e c a t s are major predators on 'Mte-eyes i n Nw Zealand urban areas. ~ e n n i k e(1955) describes t h e predation on \,kite-eyes by a 'dhite 3eron. t Predation i s p m b a j l y one of t h e most important f a c t o r s i n t h e nestmortality of lnzost species (Ri.cklefs, 1969). Tdhile it was not observed often, t h e r e a r e i n d i c a t i o n s t h a t White-eyes have evolved behavorial nteasures t o combat predation.
The existence of diversonary d i s p l a y s ,
t h e s e l e c t i v e n e s t - s i t e , t h e moving of n e s t s if t h e y a r e disturbed e a r l y i n t h e cycle, increase of singing ( t o make adults obvious) and increased c h i t t e r i n g a t fledging of t h e young, a l l point t o t h e importance of predation.
t o say.
Xhether o r not t h e pressure i s present i n Zawaii, i s d i f f i c u l t
There a r e r a t s t h a t l i v e -in many t r e e s t h a t c o u l d serve a s The
p e d a t o r s , don:: w i t h t h e mongoose, o t h e r b i r d s , c a t s , and e t c .
f a c t t h a t I d i d not observe predation o f t e n does n o t eliminate it a s
a ~ t e n t i a f a c t o r of inportance, because predation i s t y p i c a l l y seen l
seldon! i n the f i e ? ? . Few p a r a s i t e s ;.rere found. and l i t t l e e e d e n c e of disease, but a thorough search vas not cozducted,
e: In one .juvenile b i d fad da!
in June of 1972, thgre xas a moderate infection of nematodes in t h e
sut.
In one c h 4 x k , newly f l e d g d ,
I az~scovereda heavy i n f e c t i o n of
-68coccidia. The bird was very weak a d probably w o u l d have died had
I not found it.
(I took it t o the laboratory, treated i t , force fed
it f o r t w o days , and it survived. )
F!est parasites were more numerous, but probably d i d not contribute significantly t o the nesting loss. overly parasitized bg nest fauna.
9 found no evidence of chicks
There were several other instances of White-eye mortality.
In
t w o nests the young became tangled in the f i n e nest l n n and were iig
unable t o leave the nest a t fledging.
the nest, a d i n both cases they died. They w e r e found dangling f r o m
A t one nest, a young bird
f l u t t e r e d t o the ground on the day of fledging, landed head-over-heels,
and
died.
It probably injured i t s e l f when Laniirg.
The f i r s t i s discussed
Abandonment of young occurred in two cases.
on pages 49-50 i n reference t o a f f e c t s of weather on nesting behavior. The other occurred outside my study area, i n Waikiki. One chick hatched
a t l e a s t a f u l l day a f t e r i t s three siblings, and was not able t o compete f o r food.
It d i d not fledge with the other three, a d the It l o s t weight on several
parents stopped carrying food t o the nest.
days, a d w s far below normal throughout the nestling period. a
House Sparrows intempted two nests (see page
38). A t one nest,
the eggs w e r e stolen by a student on campus, and I broke several eggs
during the study.
However, those nests,-where I affected the success mortality o r success.
of t h e nest, were not used i n dete-
Table 8 Factors Contributing t o the Failure of Nests
1972-19'73
Weather Unknown arrl Miscellaneous Poor Nest Construction Interference by Animals other a than Mn Mn (excluding m e ) a
6 nests
5 nests
3 nests 3 nests
1 nest
Successful Nests (100%) Total
15 nests
33 nests
Table 9 Information on Sanded Birds and Their Returns* Total Banded Adults 3anded
Fledglings ?lumber
Banded
~ . ~ ~ U ' I I
Molting
lhmber a l i v e a f t e r 4 months
!$umber Returned
Dead
--I 972
January
0
20
February 14arch
32
6
25
0
April Yay
June July August
9
11
September 0 October Hovember
0
0
D9c ember
0
--I973
January
0
February
Fareh
0
1
April
Play
7 7
0 0
June July
Table 9 (cont. ) Total Eanded Adults Sarxled Fledglings Banded
Number
Molting
?.finimum Xmber a l i v e a f t e r 4 months
X m er u b F?eturned Dead
August --Total
3
121
3
91
0
2
-22
30
15
*
A t o t a l of 121 b i r d s were balrled over t h e 20 ,month period, a d 17 known pairs had t e r r i t o r i e s on campus, Seventeen birds caught during J u l y and August of 1972 a t Diamond Head are included i n t h e above information, a d n o l t i n g information was obtained from them.
Summary of greeding Success The o v e r a l l reproductive success of a population o r species depends on a combination of f a c t o r s , positive and negative. The i n t e r a c t i o n
of these f a c t o r s vary from season t o season, with time of season, and even from irrlividual t o individual.
In t h i s paper I have outlined many
of these f a c t o r s , a M t h e i r possible e f f e c t s on t h e Eknoa campus population, a s a representative of any lowland, r e s i d e n t i a l population of Fkite-eyes. Among those f a c t o r s t h a t could a c t i n a negative manner upon breeding success a r e weather, predators, p a r a s i t e s , food a v a i l a b i l i t y , i n t e r a c t i o n s with o t h e r spceies, and accidents.
In response t o such pressures t h e r e
are a number of p o s i t i v e f a c t o r s t h a t operate t o i n c r e a s e the breeding success.
Some of t h e s e f a c t o r s a r e present i n o t h e r passerine b i r d s ,
but I f e e l t h a t i t i s t h e combination of a l l of them t h a t contributes t o t h e success of t h e White-eyes. Following i s a b e e f summary.
1.
The o v e r a l l mortality of a d u l t s seems low, and mortality of
eggs and young i s low f o r a small passerine bird.
2.
The s t a r t of t h e season m y be somewhat adaptable i n response t o a
environmenfd f a c t o r s .
3.
4.
Sirds a m s e d e n t a ~ y ,of d e f i n i t e advantage t o a n island population. T e m t o r y s i z e i s ,related t o vegetation, allowing an e f f i c i e n t
use of the a v a i l a b l e area f o r breeding.
5.
Vegetation i n which b i r d s will build n e s t s includes a wide
v a r i e t y of species.
6.
Nests a r e d i f f i c u l t t o l o c a t e , and w e l l camouflaqed. The l o c a t i o n of t h e n e s t i s determined i n r e l a t i o n t o
7.
environmental f a c t o r s .
8,
N experience i s necessary f o r f i r s t gear b i r d s t o construct o
successful nests.
-73-
9. Development and growth a r e r a p i d , allowing several broods
per season. 10. Young a t t a i n sexual maturity within one year, allowing rapid
reprcduc tion.
I
12.
B i d s mate f o r more than one season, perhaps f o r life.
Attentiveness can be modified i n r e l a t i o n t o weather.
13.
Feeding rate of n e s t l i n g s i s somewhat adaptable, and can be
modified t o i r d i v i d u a l s i t u a t i o n s .
14.
Both parents attend t h e nest and feed the*young. Parents e x h i b i t defensive behavior t h a t has survival value
15.
16.
f o r the young. Nest s a n i t a t i o n i s comgete.
-74General Behavior of ' h i t e - e y e s
A v a r i e t y of behavior patterns a r e commonly seen i n White-eyes.
I4hile I have never observed d u s t bathing, water Sathing i s comon ard
was observed over 20 t h e s i n t h e w i l d .
A leaky a i r conditioner on
a roof was a f a v o r i t e bathing location f o r White-eyes, Ffymhs, Cardinals, Linnets, House Sparrows. also. Leaky faucets and water fountains were u t i l i z e d One bird bathing occurs once o r
!Jhite-eyes rub a g a i n s t wet foliage a f t e r a rain. Water bathing
usually stimulates o t h e r b i r d s t o bathe. twice a day i n t h e aviary.
One hard-raised White-eye f i r s t water bathed when 22 days old
became so wet it could not fly. It followed t h e o t h e r f i v e birds t o t h e water pan f o r t w o days p r i o r t o a c t u a l l y g e t t i n g i n t h e water. Sun-bathing a l s o occurs commonly i n t h e aviary. The b i r d s hang
and
from a branch o r t h e cage near a warm l i g h t , f l u f f t h e i r f e a t h e r s ,
spread
wings and tail, open mouth, and exten5 t h e neck.
t h i s behavior in wild birds, Head scratching is done over the wing.
I have not observed
I n juveniles, there may be
some trouble balancing during the f i r s t attempts.
In one hand-raised
b i d , t h e f i r s t successful overthe-wing head s c r a t c h occurred
17 days
a f t e r hatching, and i n one bird, t h e day before leaving t h e nest,
have never observed 4hite-eyes scratch urder t h e wing.
I
\iing f l u t t e r i n s i s discussed a s a component of aggression, but was
a l s o observed during c o u r t s h i p and between mated p a i r s on f i v e seperate occassions
.
P3rSaps i f analyzed more completely (i. e.
, on
film) d i s t i n c t beg f o r food,
differences would be svident.
Juveniles a l s o wing f l u t t e r as they
Pairs roost tocether a t night except when one i s on t h e n e s t , a d 1
5a7ie naver seer, n o r e t h a n two birds roosting a t any one place.
o b s 5 ~ r e droostin- on f o u r seperate occassions.
r o o s t in groups o f t w o o r thee, o r singly,
I have
I n t h e a v i a ~ y ,the
birds
-75-
In terms of yenera1 behavior, it i s noteworthy t h a t Yhite-eyes
become tame verg e a s i l y . very w e l l t o t h e avialy. Three wild b i r d s t h a t I captured a l l adapted Over the summer of 1972 I had occassion t o
keep 17 wild birds i n a cage f o r about one month, and did not loose
one bird. F'urthermore, many of those b i r d s have been recaptured since
being released, i n d i c a t i n g t h a t they had no trouble readjusting t o the
wild.
Young White-eyes a r e a l s o easy t o r a i s e , providing they a r e fed
often enough.
I have not l o s t one (six have been h a d - r a i s e d ) .
Flocking behavior i s common i n the winter seaqon, and while r e s i d e n t
birds usually remain near t h e i r home rnage o r t e r r i t o r g , I have seen
large flocks of up t o 100 birds.
of mainly juveniles o r a d u l t s .
I don't know i f l a r g e flocks are composed
Some of t h e possible functions of t h i s
behavior i s t h e easy l o c a t i o n of feeding t r e e s , and t h e observation f o r predators by many birds.
Kikkawa (1962) f o r d t h a t i n ?!ew Z e a l a d
r e s i d e n t i a l a r e a s , c a t s were t h e most itaportant predators; arsd flocking behavior by t h e birds was e f f e c t i v e i n warning off a t t a c k s from c a t s .
This flocking behavior could a l s o be important i n t h e d i s p e r s a l of
juveniles.
Pair bond formation presumably occurs during t h e winter
fl o c k i q
.
i s very common i n all species
AUopreening (= mutual preening)
of White-eyes, and Kunkel found t h a t i n
Z.
palpebrosa
and - virens 2,
it i s deperdent on dominance.
He found an aggressive o r d o x i n a t b i r d
w i l l only preen, and t h e o t h e r wiU only submit ( ~ a r r i s o n ,1969). Rowever,
in
Z.
japonica
allopreening i s reciprocal, an3 extends over t h e whole F'urthermore, I could find no s i g n i f i c a n t difference i n
body and tail.
t h e i n i t i a t i o n of allopreening i n r e l a t i o n t o dominance ersept t h a t , of t h e
six b i d s i n q y a v i a r y , t h e most subordinant engaged i n allopreenirq
more than ally o t h e r i r d i v i d u l (see f i g . 13).
This suggests t h a t it
i s r e l a t e d t o t h e hierarchy, but a more thorough a n a l y s i s i s needed.
In some b i r d s allopreening serves t o decrease aggressive tendencies
( ~ a r r i s o n ,1968; Sealander and Lame, 1961). Possibly i n my aviarg,
t h e most subordinant bird engages i n allopreening more than t h e other b i r d s t o decrease aggression toward i t s e l f by t h e o t h e r birds.
AUopreenkg i s very common i n wild and aviarg b i r d s , ard especially
b e t m e n mated pairs. Harrison (1968) suggests t h a t it may be important
in maintaining t h e pair bond.
I n White-eyes t h e r e i s no sexual dimorphism,
ard fen c o u r t s h i p d i s p l a y s o t h e r than allopree-.
probably very important in t h e p a i r bond.
.
I f e e l t h a t it is
There i s a veqy c h a r a c t e r i s t i c posture, that t h e b i d s in t h e a v i a r y
assume when s o l i c i t i n g
t h e f e a t h e r s fluffed. allopreening.
The neck i s s t r e t c h e d and a l l
Another b i r d will then fly t o t h e s o l i c i t a t i n g Q u i t e o f t e n two o r t h r e e b i r d s will be auto-
b i r d and begin t o pmsn.
preening next t o each o t h e r and this w i l l l e a d t o allopreening.
ALLOPREEN ING
Figure 13. This diaqram represents one hour observation of seven b i d s i n an aviary. Each X stands f o r a t l e a s t two bouts of allopreening, such t h a t t h e bird i n t h e left column i n i t i a t e d peening with t h e b i r d i n t h e t o p row. The b i r d s are arranged accordt o t h e i r position i n t h e hierarchy (see fig. I&), "O", "9% and "G" a r e probably males, but t h i s i s n o t known f o r sure.
:Jhite-eyes as a group have very
interest in^ aggressive behavior
This i s one area
patterns t h a t a r e e a s i l y observable in t h s aviary. t h a t might warrant more research.
There have been s e v e r a l behavorial
Z. Z. s t u d i e s on - lateralis (~ikkawa,1961o 1961b, 1969) and on - palpebrosa
( ~ u n k e l ,1962) a d I found t h e behavior of
Z,japonica
t o be v e r y
similiar t o t h a t of t h e o t h e r species.
From aviarg observations I w a s able t o o u t l i n e some of t h e f e a t u r e s
of aggressive behavior.
The displays are composed of various components
a continurn, ranging
t h a t are used i n conjunction with each o t h e r t o fo*
from t h e most fntense threatening t o submissive behavior.
Components
probably correspond t o modal a c t i o n patterns (3arlow, 1968). Components of t h r e a t behavior: wing-fluttering--wings lowered a1-d r i b r a t e d rapidly;
whine--nasal whining sound used i n conjunction with displays; chittering--scolding wing-flipping-wings c a l l s , used i n conjunction with displays : raised and lowered rapidly in a flipping
motion exposing t h e urder-wing coverts which are l i g h t e r i n color; beak-clapping--bill
i s closed rapidly producing a snapping
o r c l i c k i n g sound; probably a ritualized form of pecking; open-mouth--mouth forward look--bird opened s l i g h t l y and bill pointed towazds opponent; extelrls head a d looks directly a t opponent, present i n all
probably emphasizing t h e white eye-ring; t k e a t e n i n g displays.
Components of submissive behador: fluffing--feathers of t h e body are raised; may include only
a few f e a t h e r s , such a s only t h e c-own of the head;
avoidence look--bird
turns head amy from opponent,
These components, in combinations and context in which they a c t u a l l y occur, a r e arranged from t h e most intense threatening behavior t o t h e most s u h i s s i v e behavior i n t h e follo~wingoutline. on a v i a r y observations. These a r e based
=splay Components
Context Given i various combinations during h a c t u a l a t t a c k and chasing.
wing f l u t t e r
wj-w
flip whine beak c l a p open mouth forward look
wing f l u t t e r
whine o r c h i t t e r
open mouth f o m d look
wing f l u t t e r beak c l a p open mouth for?jard look wing flip
Preceeding o r during chase. T h i s series of components i s probably comparable t o t h e head-forward t h r e a t d i s p l a y comon t o most passerine b i r d s (Andrew , 1961)
.
Preceeding o r d u r i w chase.
beak c l a p open mouth forward look
wing f l u t t e r
Displacing another bird a t a feeding a r e a , o r preceedirq chase.
open mouth forward look
t;;,ng f l i p fon~axd look beak c l a p
Displacing a b i r d a t a feeding area, o r p r e c e d i r g chase. D-isplacing another bird.
beak c l a p forward look
Displacing a b i r d o r preventing one from landing too close7-y.
Preventins a b i r d from landing too closely.
Threatening of a dominant bird by a subordinant b i d .
open mouth forward look fluffing open mouth forward look
fluffing
forward look fluffing avoiderne l o o k
-binissive
posture.
Submissive posture, and d w i r q allopreening.
Related t o aggressive behavior i s t h e existence of a hierarchy.
Kikkawa (1961a) found evidence of a peck-right hierarchy in wintering
f l o c k s of Z . l a t e r a l i s i n Nw Zealand. e among seven m i t e - e y e s i n an aviary. s t a b l e over an e n t i r e year period, behavior a s outlined above.
-
I found a similiar hierarchy
Furthermore, t h i s hierarchy was
It was maintained by aggressive
See Figure 14 f o r a diagram of t h e hierarchy
The most submissive
established among t h e seven birds i n t h e aviary.
b i r d i n tfie hierarchy w s t h e oldest, and fed f i v e of the others as a fledglings
.
A hierarchy i n a winter f o l c k could function t o decrease t h e number of encounters between individuals, by t h e avaidence of dominant birds by subordirants.
Also t h e feeding e f f i c i e n c y of a l l but t h e most
subordinant might be increased through t h e existence of a hierarchy.
X = an a g g r e s s i v e d i s p W
that results i n eithe submissiion o r r e t r e a
= t h e displacing of one
b i d by a n o t h e r a t a feeding d i s h
0 = a c t u a l chase
STABLE HIERARCHY
Figure 1 . This diasram r e p r e s e n t s t h e h i e r a r c h y which 4 developed i n t h e avjary. It r e p r e s e n t s one hour observation, and each mark stands f o r a t l e a s t two encounters. Each b i r d i s represented by a l e t t e r . The bixds i n t h e l e f t column with t h e b i r d s in t h e t o p row, such t h a t t h e b i r d s m i n t h e t o p row gave w y t o t h e b i r d s i n the l e f t column. I a a sanz i n t h e aviary n o t sure of t h e sex, but "Om, "S" ', "G" and a r e probably males. However, t h e song d i f f e r c d from t h e a normal t e r r i t o r i a l song of wild males. "Y" w s t h e only bird t o show aggression u p t h e hierarchy. If t h i s i s a high ranking female, t h e s e r e s u l t s a r e s i m i l l a r to t h o s e obtained by Kikkawa ( 1 ~ 6 L a ) . "'0" and "I?" spent a l o t of time allopreenin5, and I t h i n k t h e y may have been a p a i r .
,
-82Adult Measurements Measurements of a d u l t birds a r e presented i n Table 10, and include t h e mean and standard deviation f o r culmen length, t a r s u s length, eye-ring width, wing and tail length. Such measurements a r e used t o
sex some b i r d species, but I did not have enough positive information
on which b i r d s were male and female t o even approach the problem,
Hanever,
in t h e case of six p a i r , i n which I was a b l e t o weigh both t h e male and
female, t h e mean difference i n weight from t h e heaviest t o the l i g h t e s t
is only 0.51 grams (range from 0.0 t o 1.1 grams).
This i s much l e s s
than t h e s t a d a m 3 d e v i a t i o n of a d u l t weight (1.55 gms), s o it appears t h a t t h e r e is probably no s i g n i f i c a n t d i f f e r e n c e in male and female weight.
Marples
(1945) fowd
a seasonal change in weight i n Zosterops
l a t e r a l i s , such t h a t t h e b i r d s weighed more during the c o l d e s t part of t h e year.
q M o r t u n a t e l y , r data a r e incomplete during t h e coldest
season here.
I c o d find no s i g n i f i c a n t d i f f e r e n c e in weights from
1972 and 1973 ( t - t e s t ) .
It has been suggested t h a t t h e w h i t e eye-ring i s used in aggressive
displays (~ikkawa ,
19614, and t h i s i s i n a c c o d with
ngr findings , Also
t h e white d e r t h e wing i s probably used i n displays such a s wing
flipping.
The green c o l o r of t h e birds seems t o be adaptive, i n t h a t
t h e b i r d s a r e arboreal.
All one has t o do i s t r y t o search f o r the
small green b i d s i n a large green t r e e t o appreciate how they a r e a b l e
t o disappear i n t h e foliage.
Table 10
Adult ~easurement * s Weight Tarsus C u b e n e Wing ail (in gms)length Length Width hwth Length (in m ) (in mm) (in m) (in mJ (in mm)
Standard Deviation
1.55
1.55
0.82
0.12
1.6
2.0
*
No significant difference in measurements from 1972 a d 1973. These measurements are from wild-caught bird.
Diet Members of t h e Zosteropidae have omnivorous feedinq habits, eating
many v a r i e t i e s of fruit, nectar, and insects.
I n Australia, White-eyes
a r e considered d e s t r u c t i v e among t h e f r u i t growers f o r t h e damage sustained t o crops, and are known by t h e connnon name of b l i g h t b i r d
(W5lkinson, 1931).
However, many f e e l t h e f r u i t eaten by t h e b i r d s i s
s m a l l compared t o t h e d e s t r u c t i v e i n s e c t s devoured by t h e b i r d s (i. e.
,
aphids and s c a l e i n s e c t s ;
Chisholm, 1908).
Y Hawaii I have made many field notes concerning t h e food t h a t h
White-eyes eat.
1 Table 1 gives a l i s t of t h e fruit ard n e c t a r that
I have included only that f r u i t
In t h e case
I have observed eaten i n t h e f i e l d .
o r n e c t a r which I have a c t u a l l y seen t h e b i r d s swallow.
of n e c t a r , it was d i f f i c u l t i n most cases, t o determine i f t h e b i r d s
were e a t i n g i n s e c t s at t h e flowers o r drinking t h e nectar, therefore,
Filly
p l a n t s v i s i t e d re,oularly a r e not included.
When drinking t h e
n e c t a r of flowers t h e b i r d s commonly s p l i t t h e base of t h e c o r o l l a with t h e i r b i l l s , t o reach t h e nectar. The tongue does not form
a tube, but i s p d r i f i e d and fimbriated both a t s i d e s and t i p (bioreau,
? e r r i n s , and Pughes, 1970). White-eyes a l s o feed commonly on flying i n s e c t s ( i , e . , termites)
t and spend much time foraging i t h e vegetation.
worms, a.nd a d u l t moths are common food items.
Inch worms, anqy
The gut content of one
juvenile b i r d found dead on t h e campus a t 0830 on June 9, 1972 included one i n s e c t from t h e order Newoptera ( ~ h r y s o p ssp, ), and ons u n i d e n t i f i a b l e i n s e c t , a d unidentified plant material.
A s t o t h e d e s t r u c t i v e a b i l i t y of T&ite-eyes concerninq f r u i t
crops, I imagine it could be great.
I have seen tanqerines s t i l l on
t h e t r e e that had no fruit l e f t , c o n s i s t i n z of only- the Lough skin.
-85Houever, Cardinals, Linnets, and ~~s were in t h e t r e e also,
feed in,^ on the f r u i t .
s,Hn toughens.
'nlhite-eyes e a t immature avacados before the
Soft skinned f r u i t such a s guavas and mulberries are
eaten voraciously by the birds,
I n the aviary-,
!4hite-eyes e a t an even wider v a r i e b j of food.
Following Eddbger (1969), I fed mainly honeywtter and high protein c e r e a l a s staples. Other food included apples, bananas, oranges, papaya,
rapef fruit, cantelope, mango, avacado, pineapple, m u l b e m , l e t t a c e ,
f i g s , potatoes, rasins,peaches, pears, plums, guava, onions, f i n y e r f r u i t , j e l l y , tangerines , syrup, bread, chocolate, cookies , hamburger, and
a variety of insects.
In other parts of the world, Zosterops has besn accused of spreading
plants.
In Australia, Gannon (1936) describes several species t h a t
Vhite-eyes and they included lcquats, The spread of lantana
'had been carried t o his yard
blackberries, lantana, asparagus, a d mistletoe.
i n Eauaii has been attributed t o the p~
(Cam, 1933), but i t appears
t h a t the Vhite-eye may have played a part also.
-86Table 11 Food Eaten by White-eyes (192-193) Comon Name
Fruit Octopus t r e e
S c i e n t i f i c Name Srassaia actinophylla Capsicum frutescens spinosum
Red Pepper
Tangerines Autograph t r e e Java Plum
Surinam Cherry
C i t r u s nobilis Clusia rosea
-
Eugenia cumini
-
Banyan
-Ficus l a c o r
Ficus -retusa Filicium decipiens
E t c h i chinensis
Banyan
Fern t r e e
Litchi
Mango
White Mulberry
Mangif era M i c a
Moms a l b a --
Mock Orange
Avacado Date Palm Allspice Strawberry Guava Guava Christmas R e r r y t r e e
IJectar Pink Shower
Murraya exotica
Phoenix sp.
dioica
Psidium cattlelanum
P s i d i m guajava Schinus terebinthifoliu.; --
Cassia qrandis Cocos sp.
Palm t r e e
Gold tree
-87Table 11 (cont ,) Common Name Nectar (cont.) Tiger C l a w S i l v e r Oak Iiybiscns Sausage tree S c i e n t i f i c Name
Erythrina v a r i e ~ a t a
Grevillea robusta Hybiscus sp. Kigelia pinnata Norantoa guianensis
African Tulip
Pink Tecoma
Spathodea campantdata
Tabebuia sp.
-88W y has t h e species baen so successful in Hawaii? h
From i t s introduction i n 1929 t o present, the Tdhite-eye has bgcome
t h e most abundant b i d i n Kawaii, more successful i n nmbers than t h e o t h e r e x o t i c s and endemics.
By studflng t h e reproductive biology and
n a t u r a l h i s t o r y , several reasons f o r t h i s become a p ~ a r e n t . When f i r s t introduced here, t h e high breeding success and low
mortality, rapid growth of t h e young (more broods per season f o r each
pair)
, and
rapid sexual maturity, enabled t h e birds t o build up a
s i z a b l e breeding population quickly.
After t h e m@d establishment,
t h e species w s able t o spread and b a d e new areas by means of winter a
flocking.
mite-eyes do w e l l in a v a r i e t y of habitats,
They are now
found. in t h e verg wet and dqy areas of t h e islands, a t a l l elevations. The b i d s readily n e s t i n a wide v a r i e t y of t r e e s and e a t an equally wide v a r i e t y of f r u i t s , nectars, and i n s e c t s . b o t i c and With t h e
endemic t r e e s and plants in Hawaii are u t i l i z e d by t h e birds.
decrease i n native plants i n Hawaii, expecially i n t h e lowlarrls, t h e b i r d s would not be adversely affected. Furthermore, members of Zosterops
c h a r a c t e r i s t i c a l l y do well i n disturbed areas.
And t h e t e r r i t o r i a l
behavior of t h e species allows an e f f i c i e n t u t i l i z a t i o n of t h e available vegetation and area.
T h i s helps t o maintain a high breeding population.
Wind and r a i n a r e t h e most important emrk-omnental f a c t o r s i n I-Iawaii, during t h e breeding season. 'rJhLte-eyes seem t o have s p e c i a l
behavior patterns in n e s t s i t e s e l e c t i o n t h a t helps t o minimize these effects. year. The b i r d s a r e sedentary, of advantage t o an i s h d population.
i s no annual migration that could carqy l a r g e numbers of them off the Them
Furthermore, nestiqg occurs d u r i n g an optinim period of the
islands.
Instead individuals remain i n one a m a t o reprcducs year
-89after year,
A few juveniles are integrated i n t o t h e population each
season, maintaining the population. Predators t h a t were present i n Japan may be absent here in S w a i i ,
a d this could contribute t o a much higher success r a t e here.
And
with t h e decrease of native b i r d s , whether o r not !dhi.te-eyes were a
f a c t o r i n t h e i r reduction, there might be many empty niches available.
Being g e n e r a l i s t s , t h e -&ite-eyes would be able t o fill some of t h e
vacancies.
Many of t h e above mentioned reasons f o r the skccess of t h e birds
i n Hawaii is c h a r a c t e r i s t i c of Zosterops i n general.
in many ways 'preadap-ked' f o r island l i f e before be-
The b i r d s were
brought here.
uction, b M s i n t h i s fanily have colonized
mom oceanic is1
s than any o t h e r family.
In l i g h t of all this,
the
phenomenal success of the species i n Eawaii i s not unexpected.
Acknowldgement s
I wish t o express my t h n k s t o SF. andrew J. Rerger f o r h i s constant
support and guidance;
D . Ernst r
S. Reese and
Dr. Robert Kinzie f o r t h e i r
h e l p i n preparinq t h i s paper;
Lamy Hirai, who assisted ne i n f i e l d
work numerous times; and e s p e c i a l l y 3. Eddie % i t h f o r h i s continu
encouragement and help i n a l l aspects of t h i s study. This project w s fund a
and x e t e p Mueller-Dombois.
W F Grant GB-23230 S
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TECHNICAL REPORTS O THE US/IBP ISLAND ECOSYSTEMS IRP F ( I n t e g r a t e d Research Program) No. No.
1 2
Hawaii T e r r e s t r i a l Biology Subprogram. F i r s t P r o g r e s s Report and SecondYear Budget. D. Mueller-Dombois, ed. December 1970. 144 p. I s l a n d Ecosystems S t a b i l i t y and E v o l u t i o n Subprogram. Second P r o g r e s s Report and Third-Year Budget. D. Mueller-Dombois, ed. J a n u a r y 1972. 290 p. The i n f l u e n c e of f e r a l g o a t s on koa (Acacia koa Gray) r e p r o d u c t i o n i n Hawaii Volcanoes N a t i o n a l Park. G. S p a t z and D. Mueller-Dombois. F e b r u a r y 1972. 16 p.
A non-adapted v e g e t a t i o n i n t e r f e r e s w i t h s o i l w a t e r removal i n a t r o p i c a l March 1972, 25 p. r a i n f o r e s t a r e a i n Hawaii, D. Mueller-Dombois.
No,
3
No. No. No. No. No. No.
No.
4
5
S e a s o n a l o c c u r r e n c e and h o s t - l i s t s o f Hawaiian Cerambycidae. G r e s s i t t and C. J. Davis. A p r i l 1972. 34 p. Seed d i s p e r s a l methods i n Hawaiian M e t r o s i d e r o s . 1972. 1 9 p .
J. L.
6
Carolyn Corn.
August
7
8
9 10
E c o l o g i c a l s t u d i e s o f C t e n o s c i a r a h a w a i i e n s i s (Hardy) ( D i p t e r a : S c i a r i d a e ) . W . A . S t e f f a n , August 1972. 7 p , B i r d s of Hawaii Volcanoes N a t i o n a l Park. 49 p.
A . J. Berger.
August 1972.
B i o e n e r g e t i c s of Hawaiian honeycreepers: t h e Amakihi (Loxops v i r e n s ) and t h e Anianiau (E. p a r v a l e R. E. MacMillen. August 1972. 14 p. I n v a s i o n and r e c o v e r y of v e g e t a t i o n a f t e r a v o l c a n i c e r u p t i o n i n Hawaii. G, A. Smathers and D. Mueller-Dombols, September 1972. 172 p. B i r d s i n t h e K i l a u e a F o r e s t Reserve, a p r o g r e s s r e p o r t . September 1972, 22 p.
No. 1 1 No. 12
A. J. Berger.
Ecogeographical v a r i a t i o n s of chromosomal polymorphism i n Hawaiian p o p u l a t i o n s of D r o s o p h i l a immigrans, Y. K, P a i k and K. C. Sung. February 1973, 25 p. The i n f l u e n c e of f e r a l . g o a t s on t h e lowland v e g e t a t i o n i n Hawaii Volcanoes N a t i o n a l Park, D. Mueller--Dombois and G o S p a t z . October 1972. 46 p. The i n f l u e n c e of SO2 fuming on t h e v e g e t a t i o n s u r r o u n d i n g t h e Kahe Power P l a n t on Oahu, Hawaii. D , Mueller-Dombois and G. S p a t z . October 1972. 12 p. S u c c e s s i o n p a t t e r n s a f t e r p i g d i g g i n g i n g r a s s l a n d communities on Mauna November 1972. 44 p. Loa, Hawaii. G. S p a t z and D. Mueller-Dombois.
No. 1 3 No. 14
No. 15
No, 16 No. 17 No. 1 8 No. 19 No. 20 No. 2 1 No. 22 No. 23
E c o l o g i c a l s t u d i e s on Hawaiian l a v a tubes. 20 p.
F. G. Howarth.
December 1972. GUnter 0 .
Some f i n d i n g s on v e g e t a t i v e and s e x u a l r e p r o d u c t i o n of koa. S p a t z . F e b r u a r y 1973. 45 p. A l t i t u d i n a l e c o t y p e s i n Hawaiian M e t r o s i d e r o s . Hiesey. F e b r u a r y 1973. 19 p. Some a s p e c t s o f i s l a n d e c o s y s t e m s a n a l y s i s . F e b r u a r y 1973. 26 p.
C a r o l y n Corn and W i l l i a m
D i e t e r Mueller-Dombois. D. Elmo Hardy and D. MuellerKent
F l i g h t l e s s Dolichopodidae ( D i p t e r a ) i n Hawaii. Mercedes D. D e l f i n a d o . February 1973. 8 p.
T h i r d P r o g r e s s Report and Budget Proposal f o r FY 74 and FY 75. Dombois and K. B r i d g e s , e d s , March 1973. 153 p.
Supplement 1. The c l i m a t e of t h e IBP s i t e s on Mauna Loa, Hawaii. W. Bridges and G, V i r g i n i a Carey. A p r i l 1973. 141 p.
The bioecology o f P s s l l a u n c a t o i d e s i n t h e Hawaii Volcanoes N a t i o n a l Park and t h e Acacia k o a i a S a n c t u a r y , John R. Leeper and J. W. Beardsley. A p r i l 1973. 1 3 p,
No. 24 No. 25 No. 26 No. 27 No. 28
H Lamoureux. .
Phenology and growth o f Hawaiian p l a n t s , a p r e l i m i n a r y r e p o r t . J u n e 1973. 62 p.
Charles
Laboratory s t u d i e s o f Hawaiian S c i a r i d a e ( D i p t e r a ) . June 1973. 17 p,
Wallace A. S t e f f a n .
N a t u r a l a r e a system development f o r t h e P a c i f i c r e g i o n , a concept and symposium. D i e t e r Mueller-Dombois, June 1973. 5 5 p. The growth and phenology of M e t r o s i d e r o s i n Hawaii. August 1973. 62 p. John R. P o r r e r .
EZPLOT: A computer program which a l l o w s e a s y u s e of a l i n e p l o t t e r . Kent W . Bridges. August 1973. 39 p.
A r e p r o d u c t i v e b i o l o g y and n a t u r a l h i s t o r y o f t h e J a p a n e s e white-eye (Zosterops i a p o n i c a i a p o n i c a ) i n urban Oahu. Sandra J. Guest. September 1973. 9 5 p.
No. 29