Nighthawks aren't really goat suckers
When I hear the sound of a passing truck and I’m not near a road, I look up. It is likely to be a common nighthawk.
Their body is about the size of a jay, and they have exceedingly long wings with a white bar at the base of the dark primaries. The rest of the body is cryptically colored. Nighthawks also make a short grating call repeated every 15 seconds or so usually in the fading light of day.
Along with its cousin the whip-poor-will of eastern North America and many other species around the world, they all belong to the order of birds named caprimulgiformes. The taxonomic name literally means “goat-milker” or “goat-sucker.” What a strange name.
It started with stories told by farmers. They observed birds flying closely about goats and other livestock in the dim light of evening. They also noted the huge mouth that seems over-sized for the bird. In the mind of someone who loves to tell stories, these observations were spun into the tale that nighthawks attached themselves to the teats of goats to feed. Of course, the real story is less fanciful. The birds were just attracted to the insects flying about the animals. The over-sized mouth is a butterfly net rather than a milking machine. People love a good tale, and the name continues to this day.
Back to the sounds they make. The grating call is their vocalization given as they forage, coursing back and forth over fields and forests. They feed like a large swallow in the evening skies. Most other goatsuckers, like the whip-poor-will and our common poorwill, remain motionless on a perch or the ground and sally out to pluck unsuspecting insects from the air.
The passing truck sound is more interesting, also described by some as a “boom.” It is produced by the wings when the bird pulls out of a steep dive. The tips of the wings vibrate, producing the sound. Why they perform this behavior is not always clear. Some have described males diving just over the head of a female as part of courtship. Others say it serves a territorial function. In my experience, birds have made the sound when I have approached too close to a nest. It was clear the bird was trying to drive me away. I say “nest,” but the two eggs are laid directly in the slightest of depressions on bare gravel.
Small numbers breed in the White City/Eagle Point area and around Emigrant Lake. Locally, one of the best places to see or hear one is at Hyatt Lake. Take a seat on the shore shortly after sunset while the sky is still lit and wait for the show, bats included.
They arrive about Memorial Day, making them the last migrant to arrive in spring, and they depart about the first of September. In late August in the drier parts of the state, it is not uncommon to encounter flocks of well over 100 birds swirling and feasting on clouds of midges and other insects over a marsh or lake in preparation for the long migration.
Stewart Janes is a biology professor, emeritus, at Southern Oregon University. He can be reached at email@example.com.