Goatsuckers in the sky

By BILL CHAISSON
Of a Feather
Yesterday I was down in that little green space between the skate park and the Sugar River in Claremont. I spotted a raptor-like bird high in the sky and then realized that there were eight of them swooping and soaring in a drifting group. The wings were long and pointed like a falcon’s and the tail was long and narrow like an accipiter’s, but they flew more like swifts or swallows. There was a fluttery, buoyant quality to the flight that raptors do not have. These birds were not rowing through the sky in search of prey like a falcon; they were feeding on the wing.

I realized with a little jolt that they were migrating common nighthawks. It has been easily 20 or 25 years since I have seen a flight of nighthawks and this is in part because their numbers have been in steady decline. There are apparently several reasons for this, but one cause is a collateral effect of a technological change. 

Before the advent of urban environments, nighthawks nested on areas of bare rock and soil that had patches of gravel. They don’t build nests per se, although their eggs may occasionally be cushioned by the presence of lichens. Masonry buildings with flat roofs became common in urban and small town environments in the 19th century. The roofs were coated with tar and sprinkled with gravel. The former would make them impervious to rain and the latter made it possible to walk on them without getting your shoes coated with tar.

These graveled rooftops became a preferred nesting habitat for the nighthawks. In addition to being plentiful and widespread, these locations had the advantage of being out of reach of many terrestrial predators, including house cats.

Nighthawks are members of the goatsucker family, Caprimulgidae. The name is derived from a legend that you can probably imagine and, yes, it is ridiculous. The other vernacular name for this family is the nightjars, which is the common name for a group of European species. The only explanation for the name that I could find was in the Encyclopedia Britannica, which claimed that these birds have “jarring” calls that surprise people during the dimly lit hours that these crepuscular birds favor. Nighthawks are related to whip-poor-wills, which are also declining in numbers in the Northeast, and are even more associated with the evening hours than nighthawks.

Nighthawks are sometimes called “bullbats,” because their fluttering evening flight resembles that of a bat and their wings make a concussive sound when they abruptly veer to change course that sounds like the snort of a bull. This kind of a noise in the air over your head in the twilight would definitely be in the category of “jarring.”

The routine call made by nighthawks on the wing is a quiet “peent,” and it used to be a ubiquitous sound in towns and cities throughout New England (and across their continent-spanning range). Now, however, New Hampshire Audubon is coordinating a project to help the species recover; it is classified as “threatened” in the state, the level before “endangered.”

The flat-topped roofs are still present, but the pea gravel is now gone. The advent of rubberized coverings has eliminated the need for the gravel. The rubber may get hot in the sun, but it doesn’t liquify like tar. The nighthawks will not nest without the gravel. Part of the Audubon project is to encourage building owners to gravel a portion of their roof whether it needs it or not. This has succeeded in attracting the birds to nest.

There are perhaps other factors that are contributing to the decline of the nighthawks (and other caprimulgids), including habitat loss in North America and poisoning on their South American wintering grounds. The North American habitat loss is in part related to fire suppression. Nighthawks are among the first species to return to areas burnt by forest fire, because they nest on the bare ground left behind and hunt for insects in the air above the open spaces that are created. 

The suppression policy is now known to have caused the intense wildfires of the western U.S., but it has also led to the decline of open-country birds of all types everywhere. The cyclical patterns of the so-called “fire ecosystems” have been disrupted nationwide. In the northeastern U.S. pine barrens, most common along the New England coast, are one such ecosystem. Controlled burns are now conducted regularly in public and private preserved areas, and this too may help restore nighthawk nesting areas … until the rampant feral cats find the nests.

The eight birds circling over Claremont were a sad echo of the hundreds of birds I used to see in migrations in my youth. These nighthawks are headed for their South American wintering grounds. They start in mid-July and the last of them depart in October. In March, they will turn around and start northward again, looking for a graveled roof.