|An English sparrow, also called house sparrow, Passer domesticus, in Brooklyn snow yesterday.|
Ever wonder how birds survive the cold winter weather? There is no question that it is hard for them, but they have some adaptations that get them through it.
Their feathers insulate them against the cold and the oils that they spread on them while preening add waterproofing. But their feet are bare ! you are saying. Like in a heat-exchange system, their blood passes through side-by-side capillaries on the way to and from the legs; incoming blood is warmed and outgoing blood is cooled. Less heat is lost that way. And they sometimes stand on one foot with the other tucked up in the feathers.
They puff up their feathers, which traps some insulating air. They can huddle together. They can sit in the sun. They find wind-sheltered places like the broad-leaved evergreen bush near my porch fence in the picture below. They sometimes perch on warm human structures, like chimneys and outdoor lights. I knew a red-tailed hawk that regularly slept on the windowsill of an old building in Manhattan -- heat leaked from the rickety windows and made it a good place to spend a cold night.
The sparrows outside my window remind me of a poem called Winter Birds, by Andrew Downing. Here is part of it:
Warm sheltered corners the cattle have chosen, Shivers the pine in its evergreen leaves; Pools by the roadside in wrinkles are frozen-- Bayonet icicles hang from the eaves. Five English sparrows, defying the weather, There in the pathway a conference hold; Ho! merry midgets in doublets of feathers! Why do you rally out there in the cold?
Little you care for the riot and rattle-- Little you heed--let the mercury fall! Brave little fighters, go on with your battle-- Here is a friend who will welcome you all! Fly to my window--I'll feed every comer-- Hail to the comrades that constancy show Loving and loyal, in winter and summer-- With us, alike, in the heat and the snow!
Interesting stuff- I'm still trying to figure out how Anna's Hummingbirds stick around here in Oregon all year round. It seems like their size would make it harder for them to keep warm.ReplyDelete
Yeah, I wonder about that too. Not only do they have a large surface-to-volume area to keep warm, but high energy demands too. I've read that Anna's hummingbirds are lingering in the north in response to available food at backyard feeders. Ironically, there is a hummingbird in New York City right now. It is fascinating the local press. I don't think it has been identified yet, but it is a Northwestern species. It's outside the Museum of Natural History and has been finding enough food and surviving the cold since mid-December. The winter has been unusually warm so far.ReplyDelete