Laura Erickson's For the Birds

Migration

(Recording of an American Golden-Plover)

If you’re out at nighttime in spring, especially on a clear night, you can often hear little peeping and piping sounds in the sky. Virtually all birds call constantly as they migrate through darkness or fog–simply because birds don’t have headlights. Although they’re all flying in pretty much the same direction, the constant peeps help them keep a safe distance apart, to avoid mid-air collisions. The FAA might take notice of this system.

Almost all small songbirds migrate exclusively at night. This allows them to spend their days feeding, and also makes them less vulnerable to hawks, which migrate by day. Also, the smaller a bird is, the more rapidly its wings must flap to keep it aloft–flying during the cool of the night may help prevent heat exhaustion.

The peak hours for night migration are between ten p.m. and one a.m., with the maximum bird numbers between eleven and midnight. Night is a treacherous time to be up in the skies without headlights. Huge numbers of birds collide with tall buildings, radio antennas, power lines, and aircraft–planes don’t make courteous little peeping sounds to warn birds away, and the loud noises planes do make, along with their powerful lights, are disorienting to creatures that evolved a hundred million years before planes. Collisions with birds have caused many fatal airplane crashes worldwide–usually when a very large bird is sucked into the jet engines. The most tragic accident involved an Eastern Airlines Electra jet taking off in Boston from Logan International Airport on October 4, 1960. It struck a flock of starlings, which clogged the jet engines; 62 of the 72 people aboard were killed. Fortunately, collisions between airplanes and birds average fewer than three per ten thousand take offs and landings, and of those, the vast majority are fatal only to the birds.

One of the most common hazards facing migrating birds is closer to home than airplanes and tall structures–picture windows kill countless birds each year. Whenever a Sharp-shinned Hawk passes over my yard, the birds in my feeders scatter in all directions. Purple Finches and Evening Grosbeaks seem to be the most common victims, although plenty of other species are also killed.

If a bird crashes into your window, chances are it’s merely stunned, and may well recover if given a chance. If it falls onto its back, it will almost surely die unless set on its feet. The kindest thing to do if a bird is stunned is to set it in a shrub or tree, where it’s unlikely to be noticed by a cat, hawk, or crow. When birds are resting, the tendons of their feet close tightly–a handy adaptation to keep them from falling out of the branches while sleeping. If you brush an injured bird’s feet against a branch, it will usually grasp it and cling, and you can leave it alone. If it’s badly stunned, you can put it in a cardboard box for an hour or two.

Taping the silhouette of a falcon or sharp-shinned hawk on a window reduces the number of fatalities, although nothing I know of can eliminate crashes altogether. If you’d like a construction-paper hawk silhouette for your window, send a self-addressed, stamped envelope to “For the Birds” at KUMD, 130 Humanities Building, University of Minnesota, Duluth, 55812.

(Recording of a Sharp-shinned Hawk)

This is Laura Erickson, and this program has been “For the Birds.”