Saturday, December 10, 2011

American Tree Sparrow

Birding the other day in the snow and cold near Circle Lake in Rice County, I came upon a flock of about a dozen American Tree Sparrows. Having seen little else during the trip, I wondered how this hardy winter visitor survives the cold. Typically individual songbirds can withstand colder weather in the winter than they can in the summer. A zero degree day in July will kill them. Small birds can also increase their metabolic rates by breaking down internal organ weight. By these and other behaviors, our small winter residents are not usually challenged by Minnesota winters. 

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