This is one of a series presented by the National Aviary, which works to inspire respect for nature through an appreciation of birds.
If I said, “Zugunruhe,” you might be tempted to say, “Gesundheit!” Actually, I’d be talking about bird migration.
Zugunruhe is a German word that describes the physiological state and associated “restless” behaviors of migratory birds in spring and fall. Scientists have learned that zugunruhe is brought about by hormones and caused primarily by changes in daylight hours. Lengthening days, as winter transitions to spring, and shorter days, as fall advances toward winter, trigger changes including hyperphagy (continual feeding) and the accumulation of fat deposits (used as stored energy for making long migratory flights).
The urge to move in a seasonally appropriate direction follows, either as night falls, as in the case of nocturnal migrants, or as dawn breaks, in the case of diurnal migrants. Nocturnal migrants mostly are small songbirds, like warblers and sparrows, while diurnal migrants include most raptors and waterfowl, swallows, swifts and hummingbirds and some larger sized songbirds, such as robins, blue jays and blackbirds.
Not surprisingly, birds that fly longer distances, to Central or South America, tend to depart or pass through Pennsylvania earlier in the fall, from August through September. Bird species that migrate shorter distances to wintering grounds within the continental U.S. do so a month or two later, in October and November.
In the Pittsburgh region right now, large flocks of mixed blackbirds (common grackles, red-winged blackbirds, brown-headed cowbirds and a few rusty blackbirds), along with European starlings, can be seen flying low over the hills or scouring the countryside for a place to rest and feed as they migrate south. Looser flocks of American robins and lines of migrating blue jays in flight also are a common sight at this time of the year.
At night, thousands of sparrows and scattered late-migrating thrushes are flying unseen overhead, the only evidence of their passage being occasional short whistles or chip notes. Their flight-calling tends to become more frequent and louder as they descend from the sky just before first light. If you happen to be up at that hour, step outside and listen overhead. After you tune out the background noise of air and ground traffic, you may hear some of the intermittent short buzzy notes or whistled “tseeps” of birds completing another leg of their migration journey.
In the grips of zugunruhe, they have flown nonstop for 12 hours and 300 miles or more. And when they need to stop over to rest and feed, it is vitally important that they are able to find good, safe sheltering habitats, such as parks and other green spaces that dot the landscape, and even well-treed neighborhoods and wildlife friendly backyards like yours.
First Published: October 29, 2014, 4:00 a.m.