Living the Scientific Life (Scientist, Interrupted)

Mystery Bird: House Finch, Carpodacus mexicanus

Posted by "GrrlScientist" on May 25, 2010
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[Mystery bird] House Finch, Carpodacus mexicanus, photographed in a backyard in Houston, Texas. [I will identify this bird for you in 48 hours]

Image: Joseph Kennedy, 28 March 2010 [larger view].

Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/640s f/8.0 at 1000.0mm iso400.

Please name at least one field mark that supports your identification.

This species has an interesting feature that provides insight into its life history — can you tell me what that feature is and what it reveals about this particular bird?

Male House Finches grow plumage that varies in color from pale yellow to brilliant red. The red is a pigment color that comes from the bird’s diet. Thus, the redder the bird, the better its diet has been since the last time it moulted. When a male bird’s color varies away from red, it is due to one of two reasons: either improper diet or physiological stress.

Interestingly, after House Finches were introduced into Hawaii, nearly all of the males are yellow in color, as is the above pictured bird. This is quite surprising as Hawaii has a lot of vegetation that could serve as food for these birds. Though the population of House Finches seems to be doing well, their discolored plumage seems to suggest otherwise.

Review all mystery birds to date.

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Comments

  1. #1 Jana
    May 25, 2010

    Cute! He looks like the yellow-morph House Finches we trapped in Hawaii. (Please note that is not an official guess though).

  2. #2 Pete Moulton
    May 25, 2010

    His color’s a bit (OK, a lot) weird for the species. My reading indicates that this is the result of his diet, but I don’t recall the exact details.

  3. #3 Bardiac
    May 25, 2010

    I’m curious about what sorts of things these guys eat to have different colors after a molt. Could the same bird, eating a different diet, molt yellow one year and reddish the next?

    I think I’ve read that flamingoes eat crustaceans that provide the molecules to make the color, but what do these guys eat? And is their diet way different in different areas?

    Does the diet thing hold for all birds? (Cardinals?)

  4. #4 Adrian
    May 27, 2010

    I am not sure that the yellow morph in House Finch is diet related as both colours occur in the same populations, (where they probably have the same diet). I haven’t seen any studies about the frequency of the two morphs in given populations, so I can’t say if there is a dietary factor involved. However I would suspect a missing “colour” component in the genetics of some individuals, although I may be completely wrong as I am not a geneticist.