CYCLE OF COLOUR CHANGES IN CATTLE EGRETS Ardeola ibis (coromandus) IN AUSTRALIA DETERMINED FROM FIELD OBSERVATIONS OF MARKED BIRDS
| Posted: |
11/08/2021 |
| Author(s): |
Max Maddock |
Colour changes in nestlings and the timing and nature of changes in colour which take place in
adults before, during and after the nesting season, as determined from field observations of marked
birds, are described for the Cattle Egret
Ardeola ibis coromandus at two Australian breeding colonies.
Nestlings have a yellow beak at hatching, which changes to yellow-tipped grey or black by about ten
days and by fledging at about 45 days, to diffuse yellow and grey. By time of independence the beak
has changed to yellow, but some retain the grey or black for up to two months after fledging. All birds
two years of age or older attained full orange-coloured breeding plumage and during courting gained
magenta face colour. First-year birds of each sex included some with typical full orange-coloured
breeding plumage (22%), some with varying degrees of pale colouration (29%), some with complete
but pale colouration (9%), while others remained white (40%). First-year birds of each pattern gained
magenta courting colour on the face, attempted to attract a mate, or mated and successfully reared
young. Wide variation occurred in the dates of onset and time for completion for both pre-breeding
and post-breeding moults. Significant variation was found in the timing of onset of magenta facial
colours and return to normal non-breeding yellow.
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