|Male northern cardinal, Cardinalis cardinalis. Click to enlarge.|
It was a cold week in New York. As I sat writing at my desk by the window I saw the neighborhood birds in another light. One of the ways birds keep warm is by fluffing up their insulating feathers; they looked like puffballs all week.
|European house sparrow, Passer domesticus.|
They have other ways to keep warm. Their feet are thermally isolated from their bodies by a network of blood vessels that cool outgoing blood and warm the returning flow. They also can stand on one leg with the other inside the warm cover of their feathers. Sone huddle together at night to share warmth. City birds are good at finding warm spots to sleep near like chimneys or lights, and on eaves. An old building I worked in attracted a red-tailed hawk on cold nights; it slept on the sill of a window that was so leaky that the perch was practically toasty.
Another thing that helps keep birds warm in cold weather is eating high calorie foods. When snow covers the ground, even the most resourceful city birds have trouble finding food. My little porch gets covered with snow but I brush off the dormant planters and put food in them: sunflower seeds, safflower seeds, peanuts, grapes, raisins, perhaps some bits of apple and whole grain bread. Below are summer photos of the neighborhood birds that have been visiting.
|A house sparrow might show up alone but is soon followed by a flock. They eat everything, including safflower seeds that they are reported to eschew. Maybe Brooklyn's house sparrows have a cosmopolitan taste for foreign foods.|
|The female cardinal has arrived alone or with a male every day.|
|American robins, Turdus migratorius, don't all migrate away for winter. They do change their eating habits. No worms are available. They disappear from lawns and go foraging for dried berries. Click here to read more details in a previous blog. One or two are spending the winter near my place; the apples, grapes, and raisins are for them. And they like an occasional nibble of whole grain bread.|