Native Animal Profile: Eastern Whip-poor-will
By Katy Gorsuch
An Eastern Whip-poor-will in Howard County
Photo by Sue Muller via Maryland Biodiversity Project. A whip-poor-will’s plumage is described as “cryptic” camouflage, which means it is designed to hide the animal.
“Then, as he wended his way by swamp and stream and awful woodland, to the farmhouse where he happened to be quartered, every sound of nature, at that witching hour, fluttered his excited imagination,—the moan of the whip-poor-will from the hillside, the boding cry of the tree toad, that harbinger of storm, the dreary hooting of the screech owl, or the sudden rustling in the thicket of birds frightened from their roost.”
– Washington Irving, “The Legend of Sleepy Hollow”
One might think of owls and bats when the temperature turns chilly, but other wingéd nocturnal creatures are often overlooked by the public. Eastern whip-poor-wills, often stylized as whippoorwills, are a native member of the nightjar and nighthawk family of birds. While nightjars can be found on every continent of the world except Antarctica, the nighthawk portion of the family is found only in the Americas. The family Caprimulgidae to which nighthawks and nightjars belong is closely related to frogmouths and potoos, who both also exhibit the nocturnal habits and similar camouflage behaviors as their cousins.
The Eastern whip-poor-will, Antrostomus vociferus, is a rare sight due to their its nocturnal nature and bark-like plumage, which allows these birds to blend into their surroundings during the day. An unusual attribute of many members of the nightjar family is their habit of resting during the day parallel to branches. The behavior is perhaps most exaggerated in their cousins the potoos of Central and South America, who may orient themselves resting parallel to the branch, with their beaks stretched up nearly vertically to best mimic the appearance of a broken branch. Nightjars exhibit similar behavior and while in near-total stillness may easily be overlooked by predators (or birdwatchers) during the day.
An Eastern Whip-poor-will in Baltimore City, Maryland (5/2/2014). Photo by Mark Johnson via Maryland Biodiversity Project.
This shows the typical stance of many nightjars parallel to the branch on which they are resting, rather than perpendicular as we are used to seeing from other birds.
Whip-poor-wills, like other nightjars, are insectivores, and may spend all night hunting on clear, moonlit nights. They possess sensitive “rictal bristles” around their mouths which may help them sense the vibrations of insects in the air in the dark. Their eyes are adapted for low light, although on moonlit nights they may alternate hunting and resting the whole evening. In fact, whip-poor-wills time the hatching of their eggs to best maximize moonlight during the growth period of their young. Eggs, which are incubated on the ground and without a constructed nest, hatch on average about 10 days before the full moon, presumably allowing parents to increase both the time they are away from the nest for foraging and the number of insects they return with as the babies grow. At about eight days old they molt into their adult coloration and around 20 days they make their first flight, at which point the mother may have already laid the eggs of their future siblings.
Eastern Whip-poor-will in Wicomico County. Photo by Jonathan Irons., some rights reserved (CC BY-NC)
Individuals are relatively small, about the size of a robin, and athletically gifted in flight. Their flight pattern is slow, but shows an ability to deliver rapid turns and fly at steep angles while hunting. Whip-poor-wills prefer surprising their prey from below, catching large moths in nearly vertical ascensions. Males will even hover in the air next to the nesting site to examine potential predators, a maneuver replicated by very few other birds. The species also possesses a tapetum lucidum, a structure shared by other nocturnal birds like owls and kiwis but also by many nocturnal mammals. The tapetum lucidum is the structure which creates eyeshine when deer appear before a vehicle at night, and it allows nocturnal animals to see more acutely in low-light conditions.
An Eastern Whip-poor-will in Garrett County). Photo by Jim Stasz via Maryland Biodiversity Project. This individual’s tapetum lucidum is reflecting eyeshine in the dark.
Most famous about the species is their call, from which whip-poor-wills get their name. Their undulating call has been the subject of cultural interest for centuries, and has been the source of their English name for just as long; they have historically been called whip-o-wills, whip o’ wills, and other variations of their call through a majority of their range. The best time to hear the classic song is from late May through early July on calm, clear nights when the moon is above the horizon. Throughout an evening, a whip-poor-will may call their onomatopoeic name up to 16,000 times! It is no wonder then that their call, echoing through their woodland habitat, would have cemented their place in the lore of the diversity of cultures inhabiting our Eastern forests.
Sadly, Eastern whip-poor-wills are declining across their native range. The best thing you can do to help these iconic native birds is to ensure they have the food they need to thrive. Whip-poor-wills are insectivores, and pesticides that reduce insect numbers also reduce the food available to them, and thus the habitat available for them to thrive in. By planting native plants in your yard, avoiding pesticides and inviting beneficial insects, and removing invasive plants where you see them, you invite not only whip-poor-wills, but butterflies and moths, bees, frogs, and other native songbirds to seek the sanctuary of your space. Even planting native plants in containers helps provide native animals with the host plants they need to flourish. Small changes to how you care for your own backyard habitat can ensure we can enjoy the call of the whip-poor-will for many more centuries to come!
Further Reading:
Cornell’s All About Birds: Whip-poor-will’s Life History
Audubon Profile: Eastern Whip-poor-will
Whip-poor-wills and Chuck-will’s-widow – including historic folk beliefs about “goat-milking”
USDA FEIS Profile: eastern whip-poor-will
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