Vocal memes in natural popultaions
of chickadees: why do some memes
persist and others go extinct?
by
Myron C. Baker
and
David E. Gammon
The black-capped chickadee
(Poecile atricapillus)
The Basics
• 8 year study
• Data obtained from 3 different regions near Fort
Collins, CO
• Studied “gargle call” (nonsong vocalization) in
subjects
– Gargle calls vary in acoustic form among
populations so essentially they are different
memes
– Looked at relationship between failed memes
and core memes
Data collection
• Individuals trapped and recaptured each
autumn/winter season for 8 consecutive
seasons
• “gargle calls” collected using sonograph
machine and displayed as sound
spectrographs
Example of a
sound
spectrograph of
a core meme
Experiment 1
• Hypothesis: Core memes are more likely to be
shared with other individuals than failed memes.
• Looked at proportion of individuals expressing
the same meme in each population
• Results: Sharing of core memes was 4 to 6
times greater than the sharing of failed memes
– Each population showed a significant
difference in the sharing of core memes and
the sharing of failed memes
Figure 3. Proportions of chickadees sharing core and failed
gargle memes in three populations. In all three populations,
sharing was significantly greater for core memes than for
failed memes.
Experiment 2
• Hypothesis: Core memes are more likely than
failed memes to be heard, and encountered in
agnostic contests, by an average bird during the
course of daily activities.
• Looked at the frequency of occurrence of 30
core memes and 35 failed memes
• Results: Core memes were expressed
significantly more often than failed memes in
each popultaion
• Figure 4. Proportions of core and failed gargle memes expressed by
chickadees in three populations. In all three populations, core memes were
expressed significantly more often than were failed memes. Data are per
core meme and per failed meme. Thus, for example, in the Lee Martinez
Park (ML) population, a given core meme represented about 9% of the
memes expressed and a given failed meme represented a little less than
2% of the memes expressed.
Experiment 3
• Failed memes were found to usually be a result
of a bird that has left the population, or a “failed
bird” (which is why failed memes only lasted 1-2
seasons)
• Hypothesis: Core birds and failed birds differ in
body size
• Results: Core birds were found to be in better
condition than failed birds (in terms of having
larger body masses), however the overall sizes
of the birds did not differ
Experiment 4
• Hypothesis: Core birds and failed birds
differ in age.
• Evaluated each chickadee’s plumage to
determine relative age.
• Results: 61% of failed birds were classified
as “young” and 70% of core birds were
classified as “old”
Conclusions
• Core memes are more likely to be shared with
other individuals than failed memes.
• Core memes are more likely than failed memes
to be heard, and encountered in agnostic
contests, by an average bird during the course
of daily activities.
• Core birds and failed birds do not differ in body
size, but possibly in overall condition.
• Failed birds and core birds differ in age.
Clips
• Genes and Memes
• Black-capped chickadee
Questions
• 1. Which type of meme persisted
throughout the study? Core memes or
failed memes?
• 2. Which memes were associated with
birds that left the popultaion?
• 3. Failed memes typically lasted how
many seasons?
– A) 0 B) 1-2 C) 3-4 D) 5 or more