Thousands of common nighthawks are streaming over the Charles, Mystic and Connecticut River valleys this week, part of an annual migration that draws crowds to spots like Mount Auburn Cemetery and Fresh Pond even as the birds have all but stopped nesting in Massachusetts. The slender, long-winged birds are on the move from mid-August to early September, following river corridors on a journey that can stretch up to 6,800 kilometres to wintering grounds in the Caribbean or South America.
The nighthawk watch is a late-summer ritual for local birders, and Mount Auburn Cemetery is one of its best-known stages, according to Cambridge Day. Watchers there once counted 432 migrating nighthawks in a single evening on August 22, 2000, and observers have reported seeing the birds on all but one watch day since 2008. Mass Audubon, the Brookline Bird Club and the Boston Birding Festival all host their own migration watch parties, and the same report notes that visitors to Fenway Park sometimes catch nighthawks feeding on moths drawn in by the stadium lights.
Those hoping to catch the spectacle should look to the sky about 30 minutes before sunset and keep watching until roughly 30 minutes after, scanning near Fresh Pond or along the Mystic River for birds on the wing. According to the City of Cambridge, Fresh Pond Reservation consists of 162 acres of open space surrounding and protecting the 155 acre Fresh Pond water supply reservoir. The nighthawks, which belong to the nightjar family and are related to whippoorwills, are active at dawn and dusk, feeding on moths, flying ants and other flying insects as they pass. At roughly 9 inches long with a 21-inch wingspan, they are built for the kind of sustained aerial travel that makes their migration one of the longest made by any North American bird, per the Maryland Department of Natural Resources.
A Courtship Sound Made by Wind, Not Voice
Male common nighthawks, formally known as Chordeiles minor, produce a resonant booming courtship sound that has nothing to do with their voice box. According to the Cornell Lab of Ornithology, the sound is purely mechanical, generated as air rushes through stiffened primary wing feathers when the bird pulls abruptly out of a high-speed dive. It is one of the more theatrical courtship displays among North American birds, and one that once played out regularly over Massachusetts backyards and rooftops…