The Birders’ Dozen Profile 9: Eastern Whip-poor-will

Dr. Jessica Outcalt, consulting bird biologist

Welcome to the Birders’ Dozen! Over the next four issues we are going to continue introducing the last few birds from Forestry for the Birds. The Birders’ Dozen are forest birds that can benefit from targeted management practices, as most are declining due to habitat loss. We’ve curated this list to cover a wide range of habitat types, from young to mature forest, open to closed canopy, or dense to non-existent shrub layers. Our goal is to engage landowners and foresters in the process of managing forests for wildlife, or “forests for the birds.”

A familiar sound of the night forest, the Eastern Whip-poor-will has appeared in literature, media, and popular culture for centuries. In the latter half of the twentieth century and recent decades, whip-poor-will populations have declined by approximately 3% per year in the Central Hardwoods region, a steep decline largely due to loss of suitable habitat. These cryptic nightjars forage on nocturnal insects, usually sallying from perches near open areas to capture insects in flight.

Natural History

Open forests are important for whip-poor-wills. Dense forests with closed canopies as well as isolated woodlots are used in much lower numbers than younger forests with canopy gaps and little underbrush. Though whip-poor-wills forage at dawn and dusk in low light conditions, they are visual predators. As such, open areas are important habitat characteristics for foraging.

While some of the birds we’ve discussed in this series have been described as “secretive” or “skulking,” the Eastern Whip-poor-will is the champion on our list when it comes to hiding. These mottled brown birds camouflage perfectly against bark and leaf litter, and are active in low light levels, which make them difficult to see, even for professional birders. However, during the breeding season—typically May through July in Indiana—these birds make their presence known with their namesake song, a clear, melodic “whip-poor-will” ringing out in the forest. Whip-poor-wills spend the winter along the Gulf Coast and in Central America, but not much is known about their migratory pathways or behaviors.

Because these birds are so secretive, relatively little is known about their biology. They are thought to be monogamous, but their courtship displays are not well known besides anecdotal reports. Whip-poor-wills do not construct nests, but lay clutches of two mottled, cream-colored eggs directly on leaf litter, generally sheltered by small herbaceous or shrubby vegetation. Both parents will sit on the eggs, which incubate around 20 days before hatching. Interestingly, egg-laying is tied to the lunar cycle so that eggs hatch roughly 10 days before a full moon. Chicks are somewhat feathered when they hatch and can run to hide from predators, but do not truly fledge until around three weeks after hatching.

Whip-poor-wills are exclusively insectivores, primarily feeding on nocturnal insects such as moths and beetles. Whip-poor-wills forage starting around half an hour after sunset and continuing into the night as long as the moon provides enough light; feeding periods typically end around forty minutes before sunrise. These birds usually forage similarly to flycatchers, by perching on a branch and sallying out to catch an insect, rather than making extended flights like bats. Specialized feathers around the beak, called rictal bristles, may help whip-poor-wills and related species navigate and catch insects more efficiently.  

Eastern whip-poor-will. Photo courtesy Matt Williams Nature Photography.

Habitat Management

Maturing forests as well as conversion of young forest to agriculture and developed land have been cited as reasons for loss of whip-poor-will habitat. In addition, whip-poor-wills are ground-nesting birds so some available shrub cover for protection from predators will benefit these unique birds. Managers have recommended creation and maintenance of young shrubland forests with open canopies for foraging and remnant large trees for perches.

Since whip-poor-wills benefit from dry forests with virtually no understory besides a few shrubs or herbaceous plants for cover, prescribed burning can create or enhance breeding habitat. Forestry techniques that open the forest canopy can foster foraging areas for whip-poor-wills as well. Since maturation of forests is one of the biggest reasons for significant population declines, whip-poor-wills depend on creation of young forests in eastern habitats.

Because whip-poor-wills nest on the ground, their nests are particularly vulnerable to predators. While native predators such as skunks, raccoons, and coyotes will eat eggs and young, domestic dogs and cats also pose a threat. Some predator activity is a normal part of a functioning ecosystem, but the extra pressure from non-native domesticated animals, especially feral cats, can be detrimental to an already threatened bird. Keeping domestic cats indoors is healthier for your cat, and can have many positive effects on your local ecosystem, even if you don’t have resources to implement more extensive management techniques.

Conclusion

The Eastern Whip-poor-will’s familiar song is a favorite sound of summer in the eastern United States. This master of camouflage is simultaneously one of the best-known singers and one of the least studied birds in eastern forests. Despite this lack of knowledge in many areas, we know they prefer forest with open understories and canopies. Though their populations are threatened by loss of habitat, creation of open woodlands can mitigate this and benefit these charismatic birds.

Special thanks to the Alcoa Foundation, the Indiana Forestry Educational Foundation, and The Nature Conservancy for their support and leadership of Forestry for the Birds.

Jessica Outcalt, PhD

Jessica Outcalt is an independent consulting biologist who worked with The Nature Conservancy to develop the “Birders’ Dozen Profiles.” She is now an Agriculture and Natural Resources educator with Purdue Extension in Grant County. She completed her BS in biology at Taylor University, her PhD in wildlife ecology at Purdue University, and is passionate about birds and getting people involved in conservation and scientific processes.

References

Akresh, Michael E., and David I. King. 2016. “Eastern Whip-Poor-Will Breeding Ecology in Relation to Habitat Management in a Pitch Pine–Scrub Oak Barren.” Wildlife Society Bulletin 40 (1): 97–105. https://doi.org/10.1002/wsb.621

Brock, Kenneth J. Brock’s Birds of Indiana – Eastern Whip-poor-will. Amos W. Butler Audubon Society, 2006.

Cink, C. L., P. Pyle, and M. A. Patten (2020). Eastern Whip-poor-will (Antrostomus vociferus), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.whip-p1.01

Delaunay, Mariane G., et al. “Anatomy of Avian Rictal Bristles in Caprimulgiformes Reveals Reduced Tactile Function in Open-Habitat, Partially Diurnal Foraging Species.” Journal of Anatomy, vol. 237, no. 2, 2020, pp. 355–66. Wiley Online Library. https://doi.org/10.1111/joa.13188.

Slover, Christina L., and Todd E. Katzner. 2016. “Eastern Whip-Poor-Wills (Antrostomus vociferus) Are Positively Associated with Low Elevation Forest In the Central Appalachians.” The Wilson Journal of Ornithology 128 (4): 846–56. https://doi.org/10.1676/15-156.1.