Sunday, November 8, 2015

American Robin

This year I took several photographs of American Robins. The first, taken on 5 May, was in the Nerstrand Big Woods State Park. The other photos were in the Carleton College arboretum on 30 October. Robins are the “most abundant and most widespread North American thrush” (Vanderoff et. al 2014).

Many people think of robins as being the first sign of spring but, even here in central Minnesota, robins overwinter. In the winter, their diet switches from worms to fruit and berries. At least in the fall, a better name for this bird might be Hackberry Thrush.
Wintering birds may not be the same populations as breeders. Usually you can tell male robins from females—the males are darker than their mates. But Canadian birds tend to be darker than robins breeding in the United States. As different populations mix during migration and winter,  birds’ sexes may not be identifiable by plumage. First-year birds also complicate matters, because their genders are often impossible to determine. As a likely local breeder, however, the robin in the first photo is likely to be a male.

Once robins molt out of their spotted, juvenal plumage, hatching year birds can be difficult to separate from birds born in previous years. The bird in the second photo was almost certainly hatched this year. Its wing coverts are pale-tipped and are buff-colored. If you look closely, the tail feathers are not worn—they have sharply pointed tips. I believe the last robin is also a first year bird. The field marks, however, are not as clear.

No comments:

Post a Comment