Where do birds spend their nights? It's a big subject, and here is what I've learned about a few local winter birds that I have studied in the field.
Even before the leaves fall, the downy and hairy woodpeckers prepare for winter by finding or digging out cavities usually high in a tree, which become their roosting holes, often vigorously defended against other hole-roosting birds. Each woodpecker roosts at night in a separate hole and will retreat there during daylight hours if the weather is bad. Deserted woodpecker holes are popular with other birds such as chickadees and nuthatches.
Black-capped chickadees are often seen during the winter in noisy flocks of about six birds formed around a dominant pair, which has bred the previous summer. A flock generally has a roosting area within its feeding territory. It is often a dense evergreen, but individual birds may also roost in small tree holes nearby.
Ducks and geese stay on open water during the night. Rock pigeons and European starlings often seek ledges of concrete buildings that have retained some heat from the day's sun. House sparrows tend to like barns and garages to get out of the wind.
Because of the safety of numbers, American crows gather in roosts. Roosts can be located by watching the direction toward which groups are flying in late afternoon or the direction from which they come at dawn. They disperse every morning in small groups to feed and then return in the same way at night.
Jim Gilbert was a naturalist for 50 years.
