A sure sign of summer in Phoenix suburbs is the return of Lesser Nighthawks that migrate north from Central and Sough America to breed and feed in the Sonoran Desert, while at the same time, many people flee to escape the heat. Between late April and October, moonlit nights and early mornings are excellent times to catch a glimpse of these ghost-like birds, as they silently dance through the air catching insects. In dim evening light, flashes of white on the tips and tails of dark silhouettes may be all you'll see, but near a lighted ball field or street light, you can get a better look at the long, pointed wings and striped plumage that make them resemble a small falcon. Nighthawks are not hawks at all, though, and lack the fierce talons and sharp beak that are primary hunting tools for birds of prey. Instead, their erratic float-and-flutter flight pattern, wide mouth, tiny beak and tiny feet are some of their most notable features.
Their dawn and dusk, or crepuscular, feeding habits and gaping mouth earned them and others in their family of birds the common name, "nightjar." Somehow they were also dubbed "goatsuckers" because they were once believed to steal milk from nannies, but there is no hard evidence for this bit of folklore. The wide mouth has also led many naturalists to speculate that nighthawks are capable of picking up their own eggs and moving them away from would-be predators, or into shade during especially hot days, but again, well-documented observations are lacking.
However, it is true that nighthawks are masters of camouflage at every life stage. As adults, striped and mottled brown and gray feathers enable them to blend perfectly with rough-barked tree branches or a
pebbly desert floor. Unless you just happen to disturb one by walking near a nest or roosting sight, it is extremely rare to see a lesser nighthawk during the day, even if you are ardently searching for one.
A female nighthawk has the additional superpower of being able to tolerate surface temperatures over 110 F as she shelters her pair of eggs or newborn chicks with the shade of her own body. The mottled eggs are laid on open ground with not other nesting material to insulate them. After eighteen days of incubation, the downy calico chick hatch and are ready to fly within a couple of weeks.
One strategy that nighthawks use for keeping cool during our scalding summers is called "gulag fluttering," which is basically a kind of panting, or evaporative cooling. The extra wide mouth, in this case, acts like a miniature swamp cooler, helping to lower body temperature. Lots of birds do this, but nightjars can also vibrate their throats to enhance the cooling effect.
Acrobatic flight, deep camouflage and extreme heat tolerance are just a few of the nighthawk's superpowers.
Since May 2005, I have written a natural history column for a neighborhood newsletter published by Jennifer Moore called "Our Big Backyard: Natural History of the Deem Hills," and since 2010, "A Suburban Naturalist."All of these columns are reproduced here. Deem Hills is a City of Phoenix Desert Preserve located just north of Happy Valley Road in north central Phoenix, and just west of I-17. The Preserve and adjacent hills comprise over 900 acres of open space with several miles of hiking trails. For more perspectives from the Deem Hills and suburban Phoenix, also check out my companion blog, Kat Tracks.
As a naturalist with a special interest in botany and plant ecology, some of my greatest passions are to explore, photograph and write about native plants. If I can spark an awareness or interest in natural history in others along the way, that is my greatest reward.