They fly about in near darkness, occasionally letting loose a buzzy call as they zigzag erratically in pursuit of fast-flying insects. In the Lower Susquehanna River Watershed, they are most frequently seen during their northward spring migration—around Memorial Day—and again in late summer during their southbound journey—around Labor Day. They spend their diurnal hours perched quietly on a tree limb, positioned lengthwise to avoid easy detection. They are Common Nighthawks
( Chordeiles minor), relatives of the Eastern Whip-poor-will (Antrostomus vociferus) and other nightjars.
Common Nighthawks begin their flights late in the afternoon, sometimes waiting until after sunset to begin foraging.
The Common Nighthawk is declining in numbers in eastern North America. Before urbanization, this species relied upon pebble beds, grasslands, burned forest, and even cliff ledges for nest sites. During the twentieth century, they adapted to sites on flat tin and gravel roofs atop multi-story buildings and became a common nesting species in cities and towns. Through at least the late 1980s, Common Nighthawks were regular breeders in Harrisburg, Pennsylvania. On warm summer nights, dozens could be seen feeding on the swarming Susquehanna mayflies attracted to the illuminated rotunda of the State Capitol Building. Increased use of rubber instead of gravel-covered roofing and decreases in flying insect abundance may be among the dominant factors responsible for the sharp decline of the Common Nighthawk as a breeding species in the lower Susquehanna valley.
As they pass through in spring and late summer, Common Nighthawks can be seen feeding wherever flying insects are plentiful. They are regular along the Susquehanna River where evening flights of multiple birds occur during the first week of September each year.
Look for migrating Common Nighthawks over woodlands and grasslands. While you’re out, check the darkening sky over any of the valley’s cities or towns. Bright lights illuminating early September football games and other sporting events attract insects… and nighthawks too!
You might see Common Nighthawks zipping around over fields used for high-intensity agricultural, usually a less-than-ideal habitat, as long as there is a source of flying insects such as a woodland, dairy farm, pastureland, fallow field, or forested streamside buffer nearby.
So look up. Common Nighthawks will only be here a short while longer, then they’re off to the tropics for the winter.