[Tweeters] Crow with Blue Beak
KevinPurcell at pobox.com
Wed Jul 18 13:15:54 PDT 2018
Difficult to say without seeing the photo but ...
I'd suggest one of the following:
After eliminating photoshopping(!).
Is there more than one photo from different angles?
Color balance issues? A specular reflection from the beak that is mostly blue sky light might make a bill appear blue (or is it black and gold?)
A more interesting speculation: A partially leucistic crow with interesting non-iridescent blue coloration in the bill?
Often blue coloration in birds and other animals (feathers, duck bills, iris coloration) is not due to a pigment but is is caused by structural preferential scattering of blue light by very small eumelanin granules or air vacuoles with an absorber of the non-scattered light behind the scatterers (a flat eumelanin layer) e.g. confirmed in a leucistic Stellar's Jay.
This is non-iridescent blue coloration (and different from iridescent coloration e.g. beetles. hummingbird gorgets and Eurasian Kingfisher feathers).
e.g. for those of you who like the literature
http://jeb.biologists.org/content/209/7/1245 <http://jeb.biologists.org/content/209/7/1245> (Geoffrey E. Hill paper resulting from a backyard birder making an interesting observation)
> A normally colored Steller's jay was observed molting from species-typical blue into all-white plumage in the back yard of a resident in Boulder County, CO, USA (B. Schmoker, personal communication; see Fig. 1). A white Steller's jay tail feather was retrieved from the ground in this backyard. A blue tail feather was collected from a normally colored male Steller's jay specimen in the Burke Museum (Seattle, WA, USA).
https://www.eng.yale.edu/caolab/papers/ADV10.pdf <https://www.eng.yale.edu/caolab/papers/ADV10.pdf> (using small angle x-ray scattering to elucidate the structure of the scatters and answer why the blue is uniform from a large number of angles).
But without the photo, it's all speculation, but if it isn't Geoffrey E. Hill might want to know about it.
> On Jul 17, 2018, at 9:05 AM, Dayna yalowicki <dlwicki at comcast.net> wrote:
> Someone on the facebook Bothell community page noticed a crow with a bright blue beak. It was in a group of other crows that had black beaks. There is a photo but it’s a closed group, so I can’t share the post. Has this been seen before and does anyone have knowledge of what this could be?
> Dayna Yalowicki
> Buy Free Range
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> Tweeters at u.washington.edu
Kevin Purcell (Capitol Hill, Seattle, WA)
kevinpurcell at pobox.com
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