August is the month of migrating nighthawks. They leave Canada by the thousands, their stiff-winged beats churning the air above the Connecticut Valley and their wide mouths seining moths and flying ants out of the late-summer skies. Nighthawks used to be common nesters in the cities and larger towns of Vermont and New Hampshire, and by late August, the local birds would join the migratory bands passing overhead, and together they would head toward the coast and then on to South America.
Nighthawks belong to the family of birds called Caprimulgids, or nightjars – their voices “jar” the night – which consist of 67 species distributed across the globe. Only eight species are found in North America. Although they superficially resemble the whippoorwill (another Caprimulgid), nighthawks can be separated from other members of the family by their long, pointed wings and lack of bristles around the mouth.
The common nighthawk of northern New England nests from the southern Yukon east to Newfoundland and south through north-central Mexico. In late August, I’ve seen nighthawks swooping over both Fenway Park and Yankee Stadium, pausing on migration to catch moths attracted to the lights above the ballparks.
I often used to see nighthawks above the campus of Dartmouth College, rowing back and forth through a river of twilight on long, falcon-like wings arched deeply back like stroking crew paddles. They’d usually arrive by early June, six or seven gathered around the Baker Library tower each evening as the tower’s white, floodlit walls drew in flying insects from all directions. The nightjars would circle, circle, circle, mouths open to catch moths.
The males would also fly up beyond the range of the floodlights and then plunge down with an audible snap. Each time one reached the end of his dive and checked his descent, his stiff primary flight feathers – the long, tapered feathers that extend from the outer half of the wing – snapped and vibrated like a tuning fork. The air boomed with these love notes. Though I couldn’t see her, the object of all this attention usually sat like a stone on a nearby gravel rooftop, watching and listening to the performances of each participant.
After several swoops toward a female, the male lands next to her. Fanning his white-banded tail, rocking back and forth and inflating his white throat, he tries to seduce her. But the courtship ritual often bores the female, and I could see the females flying away without acknowledgement or fanfare. Not to be denied, the males would pursue her back into the lights of the library tower, calling incessantly: peent, peent, peent. The entire performance was repeated more than a dozen times a night, and eventually ended in rooftop copulation. Once the bond solidifies, the female lays two eggs on the roof and begins incubation, and her mate, fresh from his nuptial triumph, will continue diving and booming until the eggs hatch.
I used to walk across the Dartmouth Green every spring in early June to see if the local nighthawks had returned from the south. I looked forward to our meetings and their annual homecoming, except when the evenings were cool or when few flying insects loitered around the floodlights, and there were no nighthawks.
By August, a sudden drop in temperature would also scatter the birds, forcing them to forage closer to the ground, away from the tower. I’d hear peents out of the blackness above the river, and I’d imagine the nighthawks sweeping above the treetops, mouths wide, swallowing insects. Our local nighthawk season is a short one – less than three months from first arrival to final departure.
But that was 20 years ago. Now, whenever I cross the Dartmouth Green in summer, I look north toward Baker Tower. Sadly, I am usually disappointed. A nighthawk’s preferred nesting spot is a flat patch of gravel that may be found on burned-over soils, along the banks of some streams, or, believe it or not, on the roofs of many older buildings. But as Dartmouth has torn down most of its gravel-roofed buildings, or as gravel has yielded to rubber as the preferred roof material for flat roofs across the Northeast, nesting nighthawks have become rare in our cities and towns. As woodlands close out pastures, and as wildfires cease to open mature forests, local nighthawks are also losing their more rural ground-nesting sites.
But they can still be seen at this time every year as they spill out of Canada and funnel down the twilit skies above our river valleys, headed for endless summer in South America.
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