[Tweeters] Crow with Blue Beak

Kevin Purcell 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

> Bothell

>

> Buy Free Range

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--
Kevin Purcell (Capitol Hill, Seattle, WA)
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