Beak deformities at Rietvlei by sdsdfqw21


									46                                                                                                 2003

                             Beak deformities at Rietvlei
                                        Graham Grieve
     344 Delphinus Street, Waterkloof Ridge 0181, S.A.

Members of the Pretoria Bird Club Ringing             likely to show adverse evidence of such environ-
Group participated in an outing at Witkop-            mental exposure than, say, a kingfisher, or the
pies in the Rietvlei Nature Reserve on 24             Three-banded Plover caught later that day.
September 2003.                                       Conversely, the kingfisher or plover might be
   Effluent from the ERWAT sewage works               less territorially restricted than the seed-eaters,
runs into the Reserve at this point. The nets         and could therefore be “diluting” the environ-
were erected close to reedbeds alongside this         mental exposure.
stream.                                                   The weaver was ringed with ring BE06162
   It was notable that two birds with de-             (Fig. 1). Its current mass (24 September 2003)
formed beaks were caught as part of the first-        was 24 g, just below the median mass shown for
light peak of bird activity. Both birds were          female Masked Weavers in Roberts VI.
photographed for record purposes (Figs. 1                 The Red Bishop was a retrap and had been
and 2). It would be interesting to know if this oc-   fitted with ring AF93103 (Fig. 2). The mass of
currence of deformity (about 16 birds per             this bird was 22 g, which is above the median
thousand based on all birds caught on this oc-        mass reported in Roberts VI for females of this
casion) is above normal, and, if so, whether          species.
this might be ascribed to the direct or second-           It would also be interesting to know if
ary effect of exposure to the effluent. (This is      there is any significance associated with the
an important question as this water becomes           fact that both birds were caught in the first
part of the raw water supply for the Pretoria         flush. Would such individuals need to work
municipal area.)                                      harder to survive than “normal” individuals?
   It should be noted that both birds with de-
formities are seed-eaters and would be less

Photograph 1. Masked weaver female                    Photograph 2. Red bishop female with
with deformed beak (Photograph by G.                  deformed beak (Photograph by G. Grieve.)

Afring News (2003) 32: 46

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