Birds go through physical, physiological and behavioral changes to prepare for the cold winters. Swanson is especially interested in these physiological changes.

“One major contribution to the birds’ physiological adjustments during the winter is their bigger muscles, which we’ve been noticing more over the last few years,” Swanson said.

While many larger birds are able to add more insulation from feathers, the smaller birds use their muscles to shiver explains Swanson. This produces heat for them.

According to Swanson, the birds that are in South Dakota year round include the Black-capped Chickadee, White-breasted Nuthatch, House Sparrow, American Goldfinch, House Finch and the Northern Cardinal. Certain birds, including the Dark-eyed Junco and the American Tree Sparrow, fly from Canada to nest in South Dakota for the winter.

These birds are true of the eastern side of South Dakota. The western side of the state closely compares to all the northern states west of the Dakotas, though Swanson notes that Dark-eyed Juncos do live in the Black Hills year round, even though they are natives of Canada. It is because of the forests in that region that attract them, said Swanson.

Swanson also notes that although an extremely harsh or extremely mild winter does not really throw these birds off, the biggest problem is when there is a vast change in a short period of time. The preparation the birds go through before a winter takes at least a week.

Swanson teaches several biology courses at USD, including Ornithology, which is the study of birds. He is currently the secretary of the South Dakota Ornithologist’s Union. A photo of Swanson is available for download at http://www.usd.edu/press/news/images/releases/David_Swanson.jpg.

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