Kelly,

Was the green sheen persistent or was it just something you noticed
at one point in time? I ask because I suspect the color could change
depending on the exact lighting conditions. This is because the color
is nearly always a result of refraction, not of any pigmentation in
the feathers.

My photo of the Barrow's Goldeneye at the Montlake Fill on Februrary
5 this year shows primarily purple, but if you look closely (click on
the top image to enlarge it) you can see a very subtle hint of green:
http://www.SongbirdPhoto.com/wordpress/?p=276

The green shows a tad bit more in my original photo, which is larger.

Here's an interesting but highly technical online scientific paper on
iridescence in nature. I have only skimmed it and have not determined
if it supports the idea that a single bird could iridesce different
colors, but it definitely supports the idea of birds controlling how
much they iridesce and in what direction (potentially signalling a
mate while evading a predator):
http://rsif.royalsocietypublishing.org/content/6/Suppl_2/S115.full

Marc Hoffman
Kirkland, WA
http://www.SongbirdPhoto.com



At 07:29 PM 3/6/2012, Kelly McAllister wrote:
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>I came upon this male goldeneye today, at Mud Bay in Thurston
>County, Washington. At first, from a distance, I thought it might
>have a round white spot at the base of the bill. But, the rest of it
>looked like a typical Barrow's Goldeneye. They I noticed a green
>sheen on the head. All of the nearby male Barrow's Goldeneyes had
>the typical purple sheen. On closer look, the one with the green
>head has a crescent-shaped loral spot, perhaps a bit reduced in size
>from what's typical. You can see this bird here:
>
><http://www.flickr.com/photos/29002564 at N08/6960686549/in/photostream>http://www.flickr.com/photos/29002564 at N08/6960686549/in/photostream
>
>I really thought I might be looking at a Common Goldeneye-Barrow's
>Goldeneye hybrid but, on closer examination, that might be a reach.
>Have others seen male Barrow's Goldeneyes with green head sheen?
>
>Kelly McAllister
>Olympia, Washington
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