The Common Poorwill
Text and Photo by Doug Backlund
"Most is likely to be gained when we walk to the edge of
established knowledge and peer over"
P.A.
Keddy, 1989
Goatsuckers. Nightjars. Caprimulgidae. Strange words that fit strange birds. The goatsuckers, also called nightjars, are a group of birds known to biologists as members of the family Caprimulgidae. As often happens, the name "goatsucker" is based on misinformation. European people once called these amazing birds goatsuckers simply because of the huge, gaping mouths that led to the belief that the birds suckled livestock. Caprimulgidae is the Latin translation for goatsucker. Although this ridiculous notion has long since been disproven, the name persists. The nightjar name apparently is based on the jarring calls of these nocturnal birds.
Four species of nightjars can be found in South Dakota. The Common Nighthawk is probably the most familiar of the group and is found statewide in summer months. Nighthawks are often active during the day, but the other three species are strictly crepuscular or nocturnal. The Whip-poor-will occurs only in the extreme southeast and northeast part of the state, in forested habitats. Whip-poor-wills occasionally can be found in the forested areas below Oahe Dam. Chuck-will’s-widow has been recorded only a few occasions and is rare at this northern latitude. Possibly the most fascinating of the group is the Common Poorwill, which can be found throughout much of western South Dakota.
The Common Poorwill is a small nightjar. Like other members of the family, coloration is cryptic. The birds blend in so well with their habitat that they are rarely seen and they will not flush until almost stepped on. The best time to find Common Poorwills is at night, when they are calling. Like the Whip-poor-will and Chuck-will’s-widow, the Common Poorwill is named for its distinctive call. The rapidly repeated "poorwill-poorwill-poorwill-poorwill" can be confused with nothing else. The birds are sometimes seen while driving on low-traffic gravel and dirt roads at night. The reddish eyeshine is usually the first indication that a Common Poorwill is on the road, from which they hunt for insects. Poorwills feed entirely on insects, mostly large beetles and moths, which they catch by short distance attacks from a ground position or a low perch. Feeding occurs primarily at dusk and dawn and during periods of night when the moon is visible and overhead. Feeding activity is associated with the lunar cycle, since the birds rely on a source of background light to spot insects flying overhead.
Poorwills are found throughout most of the western United States and into southern Canada and northern Mexico. In South Dakota, look for poorwills in rough, rocky country or near hills and buttes with abundant bare ground from May into September. The species can be found around the fringes of the Black Hills and in the forested buttes of Harding County. Poorwills can also be found along the Missouri River breaks and along the larger river breaks of western South Dakota. Common Poorwills are often considered rare birds, but poorwills can be locally common. They are not easily located and are probably overlooked by many naturalists. Common Poorwills normally nest in June, laying two eggs on bare ground. Both female and male incubate and feed the young. Very little is actually known about the life history of these birds. Their nocturnal activity, cryptic plumage, and elusive behavior make the species extremely difficult to study.
Fortunately, at least one researcher has developed techniques for capturing and studying poorwills. Mark Brigham of the University of Regina, Saskatchewan, Canada has learned some amazing facts about poorwills. Poorwills are capable of entering a state of torpor. While torpor allows survival during periods of cold or poor food availability, torpor is also a normal daily function, not just a survival mechanism. The ability to become torpid reduces energy consumption, a very valuable function for a creature dependent on nocturnal insects. The birds apparently have complete control over the process and it is not induced solely by ambient temperature. Dr. Brigham has recorded body temperatures as low as 41o F. Normal body temperature is about 104o F. so poorwills can lower their body temperature by about 63o F. Considering that a drop of a few degrees body temperature can kill a human, this is a remarkable ability. Dr. Brigham reports that one of his students located a poorwill with attached radio transmitter after a mid-August Saskatchewan snowstorm. The torpid bird was dug out from under six inches of snow. Its body temperature was 45o F. Two nights later the poorwill was at the normal routine of catching insects. In South Dakota, poorwills are on the breeding territory by late April and early May, still facing the threat of late spring snowstorms, cold snaps, and a lack of food. The ability to enter torpor allows the birds to survive those periods of wintry weather. There is a population of poorwills near Tucson, Arizona that has been shown to be nonmigratory. The poorwills in this southern area are capable of remaining in torpor for weeks at a time. Whether this is true hibernation is still questionable, but it is no wonder that the Hopi Indian’s name for the poorwill is Hölchoko, which means "the sleeping one". So, where do the poorwills from the northern portions of the range, including South Dakota, spend the winter? The fact is, no one knows.
For me, the mystery of such creatures is part of what makes nature so fascinating. A fleeting glimpse, a quick call, then nothing. Poorwills remind us that we know so little yet assume so much. It is still a thrill every time I hear or see a Common Poorwill. Perhaps you can too.
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