[Tweeters] bird eye color
jrkarr at olypen.com
Tue Apr 4 11:16:05 PDT 2017
> Tweeters -
> One more issue re eye color (not in Pileated Woodpeckers).
> During many years of banding birds in Panama, I captured and recaptured many birds from 1968-2001. My oldest record was of a Blue-crowned Motmot first banded in Mar 1983 and last captured by me in Mar 2001 (18 years later).
> Red-capped Manakins, the most frequently captured species, have dark eyes in young birds and in females of “all" ages. Mature males have white eyes. My oldest record for Red-capped Manakin was 9 years. Some females captured across multiple years developed white eyes, partially to nearly complete, as they aged. Older females (assumed by plumage and age and sometimes with recorded brood patches) often had a scattering of red feathers on the head as well. This suggests the precision of endocrine signals becomes less robust as birds age and secondary sexual characters can become more ambiguous as well.
> I do not mean to suggest this is happening in the woodpecker. Perhaps it is a factor to be considered as one tries to sort out associations between eye color and sex in birds.
> Jim Karr
"A belief is not merely an idea the mind possesses; it is an idea that possesses the mind."
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screenwriter and playwright
“It ain’t that people are ignorant, it’s just they know so much that ain’t true.” Mark Twain
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James R. Karr
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E-mail: jrkarr at olypen dot com
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