Wednesday, November 26, 2014

American Tree Sparrow

On 14 November 2014, Erika and I explored Dakota County’s new Whitetail Woods Regional Park, well worth a visit if you are in the area. The park sports many hiking trails through rolling prairie and woodlands and a small but gorgeous lake.

On this chilly day, we found a flock of a couple of dozen American Tree Sparrows. Naugler (2014) suggests this name is a misnomer, since most of these sparrows breed, often beyond the treeline, in the far north of Canada and Alaska. They winter across most of the northern United States and southern Canada.

Their winter diet includes a wide variety of seeds—about 50% grass, 40% weeds, and 10% other plants. In the summer this diet switches over to nearly 100% animal matter. Naugler (2014) further reports that captive birds drink 29.6% of their body weight in water each day and that wild birds eat snow in the winter. This species is a cold-hearty bird, because, as we Minnesotans well know, eating snow for survival often results in hypothermia in other creatures.

Two races of American Tree Sparrow are described—eastern and western subspecies. Western birds breed in Alaska and adjacent Canada while eastern birds summer across most of northern Canada. Eastern birds have more chestnut, less cinnamon-colored crowns, broader back stripes, and gray rather than whitish edges to their tails.  I suspect my photo is of an eastern bird.

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