Tuesday, May 11, 2010

Bird Colors

I have read numerous variations in Arctic tales about how the loon and raven got their colors. In one of these, initially birds were white. Raven and loon find a pail of black paint. Raven does a fine job decorating loon.  When it is loon's turn to decorate raven, however, raven is so fidgety that loon loses his patience and dumps his black paint all over raven.
Why are birds colored as they are?  Camouflage, certainly, but there is more to color than that. Biologists painted the white spots behind kingfisher bills and found that the birds could no longer aim properly for their prey.  The kingfishers were using the white spots as sighting mechanisms. [I would be interested to know if anyone has a citation for this fact.]
Often, however, why bird color has evolved is not clear.  The catch-all explanation is that bird colors attract mates. However, when researchers painted blackbirds' red epaulets black, the manipulated males found mates but had trouble maintaining territories (Searcy and Yasukawa 1983. Sexual Selection and Red-winged Blackbirds. American Scientist 71:166-174).

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