One of the signs of autumn in Missouri is the southward migration of Common Nighthawks . Nesting from Canada to the Gulf of Mexico, the species spends its winters in South America. Nighthawks will be largely out of Missouri by mid-October and will return next year in late April. They are best known for their erratic, insect-catching flights at dusk and for the loud whirring sound made by the dive-bombing males during courtship display.
I remember that my father called them "bull bats," a common name that captures their erratic flight and that low-pitched sound made when they pull out of a dive. It probably makes as much sense as "nighthawk" since they aren't hawks and don't feed so much at night as at dawn, dusk and sometimes during the day.
In the last days of summer and early fall, I have most frequently observed the migration of nighthawks while dove hunting. That is undoubtedly because dove hunting is when I stand for long periods scanning the sky for approaching birds. A migrating flock of nighthawks reminds me of the formation flights of World War II bomber aircraft that are seen frequently in war movies. The birds fly relatively low and space themselves at regular intervals across the landscape in a broad formation that is several rows deep. I have counted several dozen birds in a single flight. The record number seen at once in Missouri is one thousand!
Their overall flight habit and the broad white patch on their wings distinguishes nighthawks from similar-sized birds . They make no nest but will lay their eggs directly on soil, on stumps or on gravel of rooftops. They will perch on branches with their bodies aligned with the branch, instead of perpendicular to the branch as most birds do. This aids in concealment, making them look like a part of the branch.
Whatever cues let the nighthawks know that the year is winding down, that message has been received. We would do well to make our own preparations for the coming winter, which may or may not involve traveling to South America.