Tuesday, January 28, 2014

American Goldfinch

American Goldfinch
The American Goldfinch  also known as the Eastern Goldfinch is a small North American bird in the finch family. It is migratory ranging from mid Alberta to North Carolina during the breeding season and from just south of the Canadian border to Mexico during the winter.The only finch in its subfamily that undergoes a complete molt, the American Goldfinch displays sexual dimorphism in its coloration  the male is a vibrant yellow in the summer and an olive color during the winter months, while the female is a dull yellow brown shade which brightens only slightly during the summer. The male displays brightly colored plumage during the breeding season to attract a mate.The American Goldfinch is a granivore and adapted for the consumption of seedheads with a conical beak to remove the seeds and agile feet to grip the stems of seedheads while feeding. It is a social bird, and will gather in large flocks while feeding and migrating. It may behave territorially during nest construction, but this aggression is short-lived. Its breeding season is tied to the peak of food supply beginning in late July, which is relatively late in the year for a finch. This species is generally monogamous and produces one brood each year.Human activity has generally benefited the American Goldfinch. It is often found in residential areas, attracted to bird feeders which increase its survival rate in these areas. Deforestation also creates open meadow areas which are its preferred habitat.The American Goldfinch is a small finch, 11-14 cmlong with a wingspan of 19-22 cm  It weighs between 11-20 g  Among standard measurements the wing chord is 6.5 to 7.8 cm  the tail is 4.2 to 5.1 cm  the culmen is 0.9 to 1.1 cm  and the tarsus is 1.2 to 1.4 cm . The beak is small conical and pink for most of the year, but turns bright orange with the spring molt in both sexes.The shape and size of the beak aid in the extraction of seeds from the seed heads of thistles, sunflowers, and other plants.The American Goldfinch undergoes a molt in the spring and autumn. It is the only cardueline finch to undergo a molt twice a year. During the winter molt it sheds all its feathers; in the spring, it sheds all but the wing and tail feathers, which are dark brown in the female and black in the male.The markings on these feathers remain through each molt with bars on the wings and white under and at the edges of the short, notched tail.[12] The sexual dimorphism displayed in plumage coloration is especially pronounced after the spring molt, when the bright color of the male's summer plumage is needed to attract a mate.


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