Unlike many avian insectivores, common nighthawks seem to understand the fickle nature of a Midwestern spring. While tree swallows and eastern phoebes tempt fate in March and chimney swifts arrive by mid April, nighthawks do not turn up until early May, usually in concert with the month's first wave of warm, humid weather. After a winter in the tropics, they have no taste for the cold spells of early spring.
Once in town, they are best observed toward dusk, flapping and gliding in the evening sky with a halting, erratic style of flight. Larger and slower than swifts, they are easily identified by their white wing patches. During the day, they roost and nest on the ground (or on flat rooftops) but often take to the air after heavy rains produce clouds of insects. They are also drawn to lighted parking lots and sports fields, where bright lamps concentrate their prey.
By late August, common nighthawks begin to drift southward, often migrating in large flocks. Before the first autumn chill descends on the Midwest, most will be off to the tropics, feasting on insects and enjoying their perpetual summer.