In mid-August, one of the most elegant and least known migration flights begins. Common nighthawks, a long-distance migrant, are one of the earliest to depart their northern breeding grounds. Despite their species name, they aren't hawks and they aren't nocturnal. And, alas, they no longer are common. Nighthawks are crepuscular, a great word for the handful of species that are most active at dawn and dusk.
Formerly a bird of open country, common nighthawks shifted nesting sites to urban gravel rooftops as open habitat was lost. Forty years ago they were a common sight and sound over New Hampshire cities and ballfields lit at night as they gleaned insects attracted to those lights. Likely reasons for their decline include an increasing use of pesticides that impacts airborne insects. Gravel rooftops also are in decline as building practices shift. New Hampshire Audubon has helped launch a recovery project that includes installing rooftop gravel nesting patches in Concord and Keene.
In migration, nighthawks wend their way south in groups recognizable by a buoyant, graceful flight. They show up in the late afternoon and evening, following river valleys for the most part. Major rivers run north-and-south, offering navigation help as well as bountiful insects. When feeding is good in one area, a swarm of flying ants, perhaps, the flock reverses direction. Reports of nighthawks heading north—not south—are common.
A few years ago, at an outdoor wedding of two Audubon colleagues, a dozen nighthawks appeared in the distance, beyond the bride and groom. Throughout the ceremony, they worked the valley and hillside, traversing back and forth overhead, north and south and then north again. No doubt migrants from Canada, on their way to South America, but in no hurry.