[CT Birds] Orange finches

Chris Elphick elphick at sbcglobal.net
Sat Dec 29 10:10:58 EST 2007


Hello,

As you correctly noted, the orange (and yellow) coloration in male house finches is caused by a lack of carotenoids in the diet (carotenoids are the chemicals from which birds make red/orange/yellow pigments to colour their feathers).  This colour variation is quite common in some house finch subspecies, much less so in others.  In eastern birds it seems quite rare - at least much less common than in the birds we used to see in Reno.  A lot of research has been done on the biochemical basis for the colour differences and the ecological consequences (e.g., female house finches seem to use colour as a basis for selecting males to mate with).  

The same mechanism is probably the cause of occasional yellow individuals of other finches (e.g., purple, Cassin's), as well as variation in the brightness of male cardinals and those orange scarlet tanagers that were the subject of discussion on ctbirds earlier in the year.

The colour differences are shown in several field guides (e.g., p. 529 on the "big" Sibley guide) and there is a brief summary of the topic in the Sibley Guide to Bird Life and Behavior (p. 555).  There is also a technical (though readable) book on the topic called Red Bird in a Brown Bag (by Geoff Hill) who has done a lot of the research.  The title refers to the brown bag that is a basic house finch, that gets turned red if you add the right stuff to the diet.  If you get Birding magazine, there's a review of Hill's book (and another great book on the genetic origins of captive canary colouration - this one aimed very much at a non-specialist audience) in volume 37 (pp.  670-674).

Chris

Chris Elphick
Storrs, CT
elphick at sbcglobal.net


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