Date: 3/7/17 9:01 am
From: Steven Harder <stevenedwardharder...>
Subject: [obol] Re: Dipper question
"Why" is often a murky question when dealing with smaller aspects of morphology. The evolutionary advantage of LOTS of minor traits are unknowable. Given how dippers feed, I think the best guess for any trait in or around the eyes is that it makes immersed vision better (cuts glare?). That said, bird coloration is frequently a product of sexual selection. Murky.

Sent from my iPhone

> On Mar 7, 2017, at 8:23 AM, Bob Archer <rabican1...> wrote:
>
> Sibley states that no one knows for sure but a guess is as an aid in communication on noisy streams..
>
> http://www.sibleyguides.com/2013/04/the-white-eyelid-of-american-dipper/
>
> Bob Archer
> pdx
>
>> On Tue, Mar 7, 2017 at 8:11 AM, Linda Fink <linda...> wrote:
>> Why do Dippers, alone among birds, have white eyelids? White *feathered* (tiny feathers) eyelids at that. I can think of possible purposes but cannot find, in a web search, any definitive answer.
>>
>> Linda Fink, pondering in Grand Ronde
>> --
>>
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