More frequently heard than seen, the Eastern Whip-poor-will can be elusive for even seasoned field ornithologists. This species is well known for its distinctive and emphatic WHIP-poor-WILL call, which has aided in defining its breeding range. Even so, little is known about it's breeding biology—indeed, the first documented nests for Oklahoma and South Dakota were recorded as recently as 1980 and 1994(!), respectively ( Wood 1982b , Dean et al. 1995 ). This is a beautifully cryptic bird, but its well-camouflaged eggs and young, its crepuscular or nocturnal foraging and breeding behavior, and its large woodland territories have made it one of the least-studied breeding species in North America.
A ground-nesting species, the Eastern Whip-poor-will lays its 2-egg clutch directly on leaf litter of the forest floor. Adults remain motionless on the nest or on a roost site during daylight hours and become active only at dusk. Eastern Whip-poor-wills usually forage at dawn and dusk, but on moonlit nights they may catch moths, beetles, and other insects throughout the night. The hatching of chicks seems to be closely tied to periods of full moon so the parents can meet the energy demands of their rapidly growing young. Females do most of the incubating and brooding, and the young are fed regurgitated insects by both parents. Chicks are semiprecocial and can move from the nest site within days of hatching if disturbed. When the young molt into their black-speckled, highly camouflaged plumage at the age of about 8 days, the female often leaves them in the care of the male and initiates a second clutch within the territory.
Much of the biology of the Eastern Whip-poor-will remains unstudied. What we know about its behavior, physiology, and ecology is largely anecdotal. However, information from New York, Ontario, Quebec, and Iowa on breeding biology of single pairs ( Mousley 1937a , Raynor 1941 , Fowle and Fowle 1954 , Kent and Vane 1958 ) has helped to describe nest sites, incubation and brooding behavior, development of young, and vocalizations. Studies in Ontario using radiotelemetry have provided information on the timing of breeding in relation to the lunar cycle and on the inability of Eastern Whip-poor-wills to make use of torpor in inclement weather ( Mills 1985 , Hickey 1993 ). Research on a marked population in Kansas has provided important data on demography (CLC). Unfortunately, Eastern Whip-poor-will populations have dramatically declined over the last 50 years ( Rosenberg et al. 2016 ), which underscores the need for demographic studies in different landscapes and specific information on conservation threats faced by the species.