Common Nighthawks on the Move

Nature Notes for August 25, 2017

Just as the light is fading so that nothing is very clear, readers may see a bird with a fluttery flight passing overhead. This bird will appear as a dark silhouette with an obvious white bar on each wing. It has long, pointed wings and a long notched tail. The flight style is reminiscent of a bat, although the bird is larger than a robin.

Common Nighthawks may be seen in late August as they migrate south.

Photo © Rob Lonsberry Photography

This is the time of year when Common Nighthawks are moving south from their breeding grounds to South America where they spend the winter. Common Nighthawks breed throughout North America and into Central America.

Despite their name, they are not hawks at all, but member of the nightjar family, another odd name. At one time, they were called “goatsuckers” because of a myth that they entered barns at night and sucked goats milk.

They are a mottled brown, tan, white, and black, the perfect coloration to blend into the background when they roost and nest on the ground.

Their preferred nest sites are open, vegetation-free habitats, including dunes, beaches, recently harvested forests, burnt-over areas, logged areas, rocky outcrops, rocky barrens, grasslands, pastures, peat bogs, marshes, lakeshores and river banks. In Northumberland County, they nest in open areas of the Northumberland and Ganaraska Forests.

When we were in Saskatchewan last summer, we found them roosting on fence posts during the day at Old-Man-On-His-Back Nature Reserve. We had never seen them do this anywhere in the east.

In urban areas, they will nest on flat gravel roofs. Unfortunately for the nighthawks, the urban crows and gulls have discovered this and often depredate the nests. A nighthawk eggs is a good meal for a crow.

Common Nighthawks don’t build a nest. They usually lay two eggs which are laid directly on the ground. The young don’t stay long around the nest.

Since Common Nighthawks are active only at dawn and dusk, when visibility is poor, and they are very cryptically coloured, they are very hard to study. Both Ontario Breeding Bird Atlases commented on how difficult it was to confirm nesting of this species.

In the spring, they can often be found by their vocalisations, a “peent” given in flight. In the spring, the male has a spectacular display. He calls, circles and “booms” as he swoops down over his potential mate. The booming is caused by air passing through his vibrating primaries.

Common Nighthawks are aerial foragers. They east almost exclusively flying insects – moths, mosquitoes, flying ants – and can sometimes be seen hunting under street lights. Although their beaks aren’t very big, when they open their mouths, they have a huge gape. This is an excellent adaptation for scooping up insects from the air.

Unfortunately, like all aerial foragers, their population seems to be declining. It is listed as of “Special Concern” by Species at Risk in Ontario and as “Threatened” by Committee on the Status of Endangered Wildlife in Canada.

The causes of the decline of Common Nighthawk populations are unknown. It may be related to the decline of the insect populations on which this species preys. Other factors that may have contributed to the declines probably include habitat loss and modification. The increased predator population (specifically Domestic Cats, Striped Skunks, Raccoons, American Crows, and Common Ravens) may contribute to this species’ decline, particularly in urban areas. Other possible factors include collisions with motor vehicles and climate change.

Although Common Nighthawks do not occur in as large numbers as in the past, readers still have a good chance of seeing some in the evening as they migrate towards South America.