Why do chickadees, finches, and some robins stay in the north for the winter?
Migrating species are divided into groups of long-distance migrants, short-distance migrants, and partial migrants, which are those species in which some individuals leave their breeding areas in fall and others stay, such as some robins that switch from eating worms and insects to fruit. Many species of birds can tolerate colder temperatures as long as food is plentiful. When insects are no longer available in cold weather, chickadees switch to seeds, which are still plentiful in winter. Finches feed on pine seeds from cones that are available in winter. How long do birds live? Life expectancy is roughly correlated with size. Small songbirds may live to about 12 years. Even relatively small seabirds, such as terns, tend to have long lives for their size, actively breeding even after more than 20 years. Longevity in the wild almost never reaches the figures attained by captive birds guarded against disease and predation. Few birds die of “old age”—they continually encounter risks of pr