Very nice catch.

On a technical note the "blue phase" is the same as the "white phase" except the feathers are colored with eumelanin.

This is controlled by a single gene, MC1R, in a huge range of organisms i.g. mammals including humans, birds, fish, amphibians and reptiles. A nice example of evolution sticking to one method when it can.

http://en.wikipedia.org/wiki/Melanocortin_1_receptor
http://en.wikipedia.org/wiki/Melanin

MC1R been shown to control melanism (i.e. dark phases) in the bananaquit, the snow goose and the arctic skua.

http://rspb.royalsocietypublishing.org/content/272/1573/1633.full

> Lesser snow geese show an approximate east?west cline in morph frequency in their breeding distribution across the nearctic into the eastern tip of Russia, with blue morph birds commonest in the east. Extensive studies of fitness components in a colony at La P?rouse bay, Canada, failed to find any adaptive advantages related to plumage morphs (Cooke et al. 1995). However, geese show strong mating preferences based on parental colour, which leads to positive assortative mating (Cooke et al. 1976).

I presume this is a single mutant bird from Wrangel Island rather than one of the other populations where the "blue phase" is more common.

The melanistic gene should be dominant but the birds breed associatively so this bird might have a hard time getting a mate. But if he does find a mate his offspring will be "blue phase". So that's a good reason to check again next year to see if dark phase numbers have increased.

If you are curious about bird coloration in general get a copy of Geoffery E. Hill's "Bird Coloration" published by National Geographic. He cites the paper and shows pictures of the examples. This is an excellent book on three levels: beautiful coffee table photos and captions; good general reader text and birder hints related to an understanding how birds are colored. Makes a good gift for birders too. If the name rings a bell that is Geoffery "Ivorybill Hunters" Hill. His day job is as a prof at Auburn University in AL researching bird coloration.

On Feb 16, 2011, at 11:59 AM, Stark, John wrote:

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