Bird of the Week: Common Nighthawk

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During the day, Common Nighthawks often roost in plain view. This adult male was photographed near Adel, Lake County, OR on 29 July 2008 (Photo by Dave Irons).

In the coming days, our latest spring migrant, the Common Nighthawk, will finally make its way into the Pacific Northwest. Like the "Boys of Summer" referenced in the the late-90's song by Don Henley, nighthawks are birds of summer in higher latitudes. Their distinctive nasal "peents" are rarely heard in most of Oregon before the first of June.

Nighthawks and their relatives are members of the order Caprimulgiformes. The origin of this scientific name literally means "milker of goats" (Cleere 1998). Like other crepuscular creatures, which don't become active until the last few footcandles of daylight fade away, nighhawks and nightjars are the subject of colloquial lore. Traditionally, many believed that these birds suckled milk from goats and other livestock during the night. In fact, nighthawks and nightjars subsist almost entirely on a diet of insects and, so far as anyone knows, they don't ever suckle livestock. And yet, if you look in your field guide, you will still see them referred to as "goatsuckers."

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Hatch-year Common Nighthawks, like this juvenile photographed at Malheur NWR, Harney Co., OR 29 August 2009, are decidedly more buffy and gray than adults. They have shorter tails and shorter, more rounded wings than adults. In this plumage, they may be confused with the more southerly Lesser Nighthawk (Photo by Dave Irons).

As one might expect from a family of highly insectivorous birds, nighthawks and nightjars are primarily tropical. They migrate into temperate zones only during the breeding season, although some individuals may go into a torpor (a hibernation-like state) and remain through the winter months on or near their breeding grounds. Of the 119 species of Caprimulgiformes listed by Cleere (1998), only eight are known to occur somewhat regularly in the U.S. and Canada and three of those barely reach our southern boarders. The Common Nighthawk is the most widespread  and most northerly breeder of the five species with extensive ranges in North America. They can be found from coast to coast during the summer months and their breeding range extends well north into Canada -- as far as southern Yukon in the west, southern Labrador in the east, and the northern reaches of the "prairie" provinces in the center of the continent (Poulin et al. 1996).

If you see a Common Nighthawk up close, you will likely notice that they have a comparatively tiny bill. However, this bill belies a yawning basket-like gape that can be opened wide as they fly about in pursuit of moths and other flying insects. Studies have determined that nightjars have a highly-evolved jaw mechanism that allows them to open their mouths both vertically and horizontally (Cleere 1998). In flight, they are more like a butterfly or a bat as they feed, with constant darting and changes of direction. One of the colloquial names for Common Nighthawk is "bullbat," again referencing the traditional beliefs about this group of birds.

Many species of nightjars nest or roost on the ground, where their cryptic coloration allows them to easily blend in among the dried leave litter. During the nesting season, male Common Nighthawks do a "booming" display, performing steep dives that result in an audible rush of sound as air passes through the primaries at the bottom of the dive. The sound produced is a descending hollow, reedy "fffooom" with a slight rise in pitch at the end. This sound has a humming or vibrating quality that is sort of like what is created when you purse your lips and blow on the edge of sheet of paper (though not nearly as high-pitched).

Thoughts of Common Nighthawks evoke memories of warm summer evenings, the buzz of insects, sitting around a campfire toasting a marshmallow, and the welcomed interruption of a "peent" overhead...a sound I don't hear as often as I'd like.

Literature Cited:

Cleere, Nigel. 1998. Nightjars: A Guide to the Nightjars, Nighthawks, and Their Relatives. Yale University Press, New Haven, Connecticut.

Poulin, R. G., S. D. Grindal and R. M. Brigham. 1996. Common Nighthawk (Chordeiles minor), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/213doi:10.2173/bna.213

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