Monday, February 15, 2010

American Goldfinches

This morning for the first time in 2010 I was able to band birds.  About 200 American Goldfinches swarmed at the banding station.  I banded a dozen.  I also caught a single House Finch and Pine Siskin. Many non-banders are unaware that, in the field, you call tell the sex and often the relative age of most basic-plumaged (winter) goldfinches.  I thought I would share these photos with you.  (The photos were taken against a snow drift, hence the white backgrounds.)

Male and female American Goldfinches can be told apart by their wing color: jet black in males, charcoal in females.
Female American Goldfinch with charcoal-colored wings.  Because it is now February, this bird is aged as AHY, or After Hatching Year.
Compare this male goldfinch's jet-black wing with the female's charcoal wing.  We can take the aging of this male bird further than we could the female.  Note the dull shoulder color of this male: this color indicates it was born just last year, hence a SY or Second Year bird.

Compare that color to the bird below.
Since it takes two years of Goldfinches to molt into these bright yellow shoulders, it is aged as ASY, or After Second Year.  Often this color can be noticed in a male with a folded wing.
Because goldfinches of all ages suffer equal mortality, by this time of year anyway, one would predict dull-shouldered SY birds will outnumber older, brighter-winged birds.

3 comments:

  1. this goldfinch sexing and aging lesson is very very interesting! Please keep up these brief seminars, I love them!
    Pete Hoeger, Hutchinson

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  2. Thanks, Dan! I agree with Pete! Please also keep the MOUnet & MNbird lists apprised of your posts as well. I have noticed some of the differences you mention but never bothered to sort out what it meant. Now I will note this detail from now on.

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  3. I love that photo of the ASY male with the wing stretched out and looking at it.

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