For some people, memories of childhood summers include Common Nighthawks flying overhead. Seeing their quick, looping flight and long, pointed wings with distinctive white bars were delights of being out after dark on nice summer evenings. But Nighthawk sightings in Illinois have declined, no longer a certain part of summer landscapes.
Common Nighthawk is a bird much-enjoyed by birdwatchers and non-birdwatchers alike. But Nighthawk numbers are in decline for several reasons. One is changes in how buildings are constructed. In natural habitats, Nighthawks nest on the ground, in gravelly places such as beaches or rocky outcrops. In cities and suburban areas, they often used flat, gravel roofs.
At one time, many industrial buildings had flat roofs covered with pebbles, which made good nesting sites for Nighthawks. The roofs were isolated from disturbances, and pebbles provided camouflage for the birds and their speckled eggs. But changes in construction practices have made flat, pebble-covered roofs less common.
Common Nighthawks, like many creatures, also may suffer from the harmful effects of pesticides used by people. According to the National Wildlife Federation, populations of many types of insect-eating birds are declining. In some places, populations of Common Nighthawks, Chimney Swifts and some swallows have dropped by more than 70 percent in 20 years.
These species all feed on flying insects, the numbers of which have decreased with pesticide use. In addition to reduced food supplies, insect-eating birds also may be harmed by pesticides accumulating in their bodies. A recent blog post by Christopher Cudworth eloquently describes how pesticides and other human influences, such as climate change, may be affecting Nighthawks.
Now that fall migration time is here, Illinois birdwatchers will look up and scan the sky for Nighthawks. But, with rare exceptions, they won’t see many; nor will they hear the Nighthawk's unique ‘peent’ call. The decline of Nighthawks illustrates how environmental disturbances add up and threaten the survival of even common, widespread species.