Along with other aerial insectivores that capture insects while in flight, Common Nighthawks are of high conservation interest in Wisconsin because they are a declining species, a similar situation to that of Chimney Swifts. Nighthawks are distinctive in their flight style, steep courtship dives, and habit of nesting on flat roofs, as well as in open-country habitats with some bare soil. It can be difficult to confirm breeding, especially in urban locations due to the inaccessibility of rooftop sites, so here we offer tips for finding and confirming this unique species in your Atlas block.
Region: Entire state. eBird Range Map
Time of Year: Common Nighthawks arrive in Wisconsin in mid to late May, with the majority arriving in late May. Nesting birds will soon begin their booming courtship displays. Breeding codes may be recorded into mid-August, when southbound migration begins in earnest. This migration peaks from late August through mid-September.
Breeding Guideline Bar Chart: (Full chart is on atlas handbook webpage)
Time of Day: Common Nighthawks are nocturnal and crepuscular – they start their foraging before sunset, continue into the night, but can occasionally be seen flying post-dawn. They could be seen feeding young during any dates from June into early August. If flushed during the day, they will fly off and return if not repeatedly disturbed. Bottom line for atlasers – visiting appropriate habitats at dawn, dusk, or bright moon-lit nights is key!
Focal Habitat: The most productive natural habitats include open barrens on sandy soils, sometimes with scattered jack or red pines and always including some bare ground. Nighthawks will nest on bare substrate such as sand, dirt, gravel, or bare rock. Other sites include grasslands, or occasionally fields under cultivation that have some bare patches, extensive burned areas, or rarely open bogs. Large logged tracts may be used, and nest-site records even exist from between railroad tracks. Nighthawks also nest on flat roofs in small towns to large cities, especially roofs with adequate surfaces. The once common tar-and-gravel roof top substrate is being replaced by a rubberized covering on many new flat roofs; this seems to be less well-tolerated by nighthawks. In the northeastern U.S., there are efforts underway to provide a gravel pad for nighthawks on some new or re-constructed roofs; so far limited success has been reported.
Two eggs are laid on the ground, and no actual nest is built. Incubation is done solely by the female. Young nighthawks hatch after approximately 18-20 days of incubation. They are covered with sparse patches of down. Both parents feed the young by regurgitating their insect prey, and feeding takes place at either dusk or dawn. Nighthawks consume only flying insects, caught on the wing.
Special Methods: It is imperative to visit suitable habitats in your block around dusk or dawn from late May into early August. It will be easiest to achieve a “Probable – C” code by listening for the “booming” of male nighthawks during this time. Males fly up to a height of 30 meters or more, and dive quickly, then fly upward again. During the descent, the outer primaries of the wing are under pressure and thereby produce the resounding boom. Confirming this species is difficult without some good luck.
Code Guidance: Use C for nighthawks performing aerial courtship displays accompanied by the “booming” display sound. Birds giving the standard “beeer” flight call over suitable habitat outside of the migration window should receive an “S” code. While technically not a “song”, this sound does function in territorial display by males. Be cautious about using N for visiting probable nest site. Only use N if you observe a nighthawk repeatedly alight in a specific location on the ground or flat roof. In some cases, you may be able to view the nest with eggs or young, which would warrant NE or NY, respectively. In barrens or burned-over areas, nighthawks nest on the ground where you may flush one by accident; be careful not to tread on eggs or flightless young. If an obviously juvenile bird is found away from the nest, then FL would be appropriate.
Other Species: Dawn and dusk surveys for Common Nighthawks may also be productive for Chimney Swifts, especially in developed areas. Swifts, like nighthawks, are declining aerial insectivores of high conservation concern. In barrens, dawn or dusk surveys often yield E. Whip-poor-wills, Amer. Woodcock, and other species.
Confusing Species: Few species can be visually confused with nighthawks. Look for the white bar on the underside of the wing, across the base of the primaries. Their moth-like, stalling flight and particularly their steep dives are distinctive aspects of summer behavior. Beware their “beeer” flight call is often mistaken with the “peent” call of the American Woodcock, which is typically more harsh, given from the ground while perched, and predominant from mid-March to mid-May before nighthawks arrive.
More information about Common Nighthawks:
Birds of North America (subscription required)