When the winter comes knocking in New York, certain birds stay the course and make the season less severe for the rest of us. It is clear that winter is on the doorstep if not actually in residence. Like people each bird species has its own coping mechanisms for surviving the chill.
First, of course, feathers can be remarkably insulating. Thor Hanson, in his charming book “Feathers: the Evolution of a Natural Miracle” gives the example of a small bird that winters in Maine which, in season, has shown a skin temperature 140 degrees higher than the ambient air.
Not all birds are so well endowed but most “know” enough to change their geometry. We lose heat through the surface of our bodies, and the sphere has the smallest surface for a given volume – so by configuring their bodies into a more bulbous form, birds can minimize their heat loss. The first photo above shows the Hermit thrush just a couple of weeks ago; the others display winter configurations.
Opening photo: Hermit Thrush in the fall
All photos by Fred R. Cohen. See more of his work on his website.