A nighthawk is a medium-sized bird that flies at dawn and dusk, catching insects in mid-air with its wide, gaping mouth. Despite its name, nighthawks aren't hawks at all: they're related to a bird called the whip-poor-will. They have mottled brown and gray feathers that camouflage them perfectly when they rest on tree branches or even gravel rooftops during the day.

You might see nighthawks swooping through the air on summer evenings, making sharp turns as they chase moths and beetles. Male nighthawks make a distinctive booming sound during their courtship dives, created by air rushing through their wing feathers as they pull up from a steep plunge.

The word nighthawk can also describe a person who stays up late or works during nighttime hours. A security guard working the overnight shift might be called a nighthawk, or you might say that your older sister is a nighthawk because she does her best thinking and studying long after everyone else has gone to bed. Like the bird hunting insects at twilight, a human nighthawk is most active when others are sleeping.