BY KIERAN LINDSEY, PhD
I wonder if Henry knew that not everything that shoots into the air falls back to Earth.
I’m not denying the sovereignty of gravity but if the arrow is a male common nighthawk (Chordeiles minor) hoping to impress a potential mate he’ll shoot swiftly into the air like a projectile, tip into a steep dive as if preparing to pierce the planet’s crust, but then just before impact…
…he’ll lower the flaps, make a U-turn mere meters from terra firma, and sling back skyward from whence he came like a boomerang on the rebound, the wake of disrupted air skidding over wingtips with a boom reminiscent of a supersonic F-22 Raptor.
That comparison to a Raptor, whether manufactured by Lockheed Martin or Mother Nature, is pure metaphor. The nighthawk is neither hawk nor nocturnal. Active at dusk and dawn, plus about 60 minutes before and after the sun slips from view, you won’t see this bird’s silhouette set off against the moon. By full darkness they’re wheels down and back home in the hangar, resting up for the next day’s sorties.
Nighthawks are traditionally positioned taxonomically in tight formation between owls and swifts, although recent DNA sequencing results have raised more questions than they’ve answered about the stealth origins of the Caprimulgidae family of aviators (aka nightjars).
The hypothesized connection to owls is based primarily on plumage, a shared color palette (whites, blacks, greys, browns and buffs), and cryptic feather patterns. The link to swifts appears less superficial to my eye, owing to similarities in posture, build, and aerodynamics. Both swifts and nighthawks have flattened heads, long slender wings, and specifications that disqualify perching upright, as is the custom of their feathered brethren.
Like swifts, nighthawks are poorly equipped for life on Earth, with small, weak legs and feet that barely tolerate their landing gear duties. But the transformation at take-off from klutz to accomplished aerialist is abrupt and undeniable, stark enough to make you question how moored and mobile forms could be one and the same creature.
The nighthawk is built to rule the heavens, and it’s a big sky indeed, poised above the better part of two continents in two hemispheres. Of all the migratory birds who breed in North America, the common nighthawk is among the most well-traveled. The aerial version of a road warrior, moving back and forth with the seasons as far as 8,000 miles one way, nearly 1/3 of our planet’s circumference, from the northern-most edge of their breeding range in the Yukon and Northwest Territories of western Canada to the La Plata región of Argentina on the east coast of South America. Now and then, an individual will divert from the standard flight path for a stopover in the Azores, the Faroe Islands, Iceland, Greenland, or even all the way across the pond to the British Isles.
Of course, during these long hauls they grab their meals on the fly… but that’s just standard operating procedure for a nighthawk. It’s the logistics of refueling, for the day or for an expedition, that observers will find startling and astonishing. The abbreviated bill is but the latch that unlocks a gaping maw of mouth, a funnel with which the nighthawk scoops winged insects out of thin air.
Nighthawks forage in the airspace from knee-high over ground or water to 500 feet of elevation or higher but they’re not vacuuming willy-nilly. Despite their habit of feeding under low light conditions, at the dawning and the dimming of the day, they appear to locate prey primarily by sight. In fact, there’s a special structure in the eyes of a nighthawk that reflects light back to the retina, amplifying limited illumination… kind of the equivalent of bionic night vision goggles.
Courting happens with the male aloft, as described above. The female watches his aerial antics from a birds-eye view or from a stationary point below. Nighthawks are frequent flyers but they aren’t into that Mile High Club stuff. Copulation takes place while grounded and, naturally, raising a family is one of life’s activities that even a nighthawk can’t do while airborne.
When nesting, this species prefer to put a little distance between itself and its kin, although they’ll tolerate the presence of other birds. Females are competent and attentive mothers but they’re not really into homemaking. Little time or effort are spent on decorating in preparation for the pitter-patter of feet so small they don’t make much noise anyway. She just chooses or creates a shallow dimple in an otherwise level expanse of sand, gravel, stone, or soil the deposits two freckled eggs into this austere nursery.
Her nascent progeny blend into their surroundings so well one wonders how nighthawk parents don’t end up caring for a couple of worn stones by accident. In all honesty, Mom and Dad pretty much disappear from view when settled on this substrate as well, so maybe nighthawk eyes can perceive subtleties of pattern that are lost on human peepers.
The eggs are incubated mostly by the female. The male stands guards (okay, “stands” may be an exaggeration due to his aforementioned lower body anemia so let’s say he reposes) from a nearby tree or other observation deck — the location changes daily — diving, hissing, or aiming a sonic boom in the direction of any perceived threats. While she’s on the nest he’ll help keep up her strength by sharing (i.e., regurgitating) part of his last meal. He’ll also take an occasional turn on the eggs when his mate needs a break to stretch her wings and have a meal that isn’t second-hand.
Approximately three weeks later two semi-precocial offspring push out of their shells and into the world with eyes wide- or half-open. Once their down dries and they’ve taken on some fuel, they’ll start taxiing up and down the runway but no takeoffs quite yet. As soon as they stop to rest they fade into the background again.
Three weeks from hatching the youngsters will attempt their first flight. Seven to ten days later they’ll be proficient pilots. By day 30 they’ll wave goodbye to their folks, who have probably started work on a second brood, and their siblings. At the ripe old age of eight weeks they’ll be nearly identical in appearance to an adult… a little paler in color, perhaps, with a smaller white wing-patch but boy-howdy kids grow up fast, don’t they?
Since the early part of the 20th century, if not before, nighthawks have lived and worked and raised families in urban and suburban environments. Like bats, they’re drawn by insects attracted to the bright lights of a big city. Thanks to stadiums, streetlights, and billboards, shopping for groceries is quick and easy. Moreover, when flat gravel roofs were in vogue with architects and builders, they inadvertently created quasi-gated communities with a view where nighthawks could raise their kids with fewer predatory concerns than they face on land. In response, nighthawk numbers climbed. Few of their human neighbors took much notice but they certainly benefited from having neighbors who curtail mosquitoes and other six-legged annoyances.
Male common nighthawk near nest on the ledge of a building roof in 1922.
More recently, gravel roofs have fallen out of favor, replaced by rubberized membranes that increase energy efficiency but are completely unsuitable for nesting nighthawks. Combine the resulting decrease in reproduction rates with an increase in mortality due to pesticides, road kills, power lines, cell towers, wind turbines, and the impacts of climate change… is it any wonder the common nighthawk population is in steep decline?
I’m afraid it’s going to take more than aeronautic prowess for nighthawks to pull out of this dive. Efforts to provide gravel pads in rooftop corners, while well-meaning, are far too limited in scale at this point to provide much lift.
I think anyone who appreciates the beautify and virtuosity of an impromptu summer evening airshow can agree that’s an arrow to the heart.
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