Birds
Nightjar
Caprimulgidae · also called nightjars, goatsuckers
A nightjar spends the day lying so still and so perfectly camouflaged on bark or bare ground that most people never see one, even standing right beside it. At dusk it lifts off and hunts moths with its mouth open wide, a churring call rattling across the heath through the night. Older folklore had it drinking milk from goats — it was only ever after the insects gathered around them.
Overview
Nightjars are the family Caprimulgidae, nocturnal insect hunters of open and semi-open habitats worldwide. They catch moths and beetles in flight with a mouth that opens far wider than the beak suggests, and their mottled brown and grey plumage is near-perfect camouflage against bark, leaves, and stony ground by day.
No nest, no colour, no defence but stillness
A nightjar lays its one or two eggs directly on bare ground, with no nest at all, relying entirely on camouflage — and will carry the eggs off in its mouth if disturbed. The name “goatsucker” comes from an ancient myth that the birds milked livestock at night; they were only ever hunting the insects drawn to the animals.
Voice and torpor
The European nightjar’s long mechanical churring call can run almost unbroken for minutes. The North American common poorwill is the only bird known to enter prolonged, hibernation-like torpor, dropping its body temperature for weeks at a time in cold weather — a behaviour Hopi tradition had already named it for, long before scientists confirmed it in the 1940s.
Status
Least Concern overall, but declining in places — the European nightjar has lost much of its heathland breeding habitat to development and forest succession, and ground-nesting leaves all nightjars vulnerable to disturbance and introduced predators.
Nightjar: common questions
Why is the nightjar also called a goatsucker?
The name comes from an old folk belief, already recorded in ancient Greece, that these birds flew into barns and pastures at night to suck milk from goats, supposedly leaving the animals blind or dry. The real explanation is far simpler, in that nightjars were drawn to livestock because insects, especially moths and flies, gather around grazing and stabled animals, and the birds were hunting those insects on the wing, not touching the goats at all. The myth was persistent enough that it is preserved today in the family's scientific name, Caprimulgidae, which literally means goat-milker.
How does a nightjar catch insects with such a small beak?
The beak itself is small, but the mouth behind it opens astonishingly wide, far beyond what the beak's outline suggests, turning the whole face into an effective net. Flying with its mouth agape through a cloud of moths or beetles, a nightjar relies on this huge gape, often edged with stiff bristle-like feathers that may help funnel insects in or protect the eyes, to scoop up prey directly out of the air, sometimes catching several insects on a single pass, rather than picking off one insect at a time with the tip of the bill the way most birds do.
Why don't predators find nightjar eggs and chicks more easily?
Because everything about them is built to be overlooked rather than defended. The eggs are laid straight onto bare ground with no nest to draw attention, and both the eggs and the sitting adult are patterned to match the exact leaf litter, gravel, or bark colour of the site, so a predator or a person can walk within a step of an incubating nightjar without noticing it. If a nightjar is disturbed, it will often perform a broken-wing distraction display to lure a predator away, and in some situations can even carry its eggs a short distance in its mouth to a safer spot.
Can a bird really hibernate like the poorwill?
The common poorwill of the western United States and Mexico is the best-documented case, entering a state of torpor in which its body temperature can drop to close to that of its surroundings and its metabolic rate falls dramatically, sometimes for weeks at a stretch during cold snaps when flying insects are scarce, tucked into a rock crevice. This is not full mammalian-style hibernation lasting an entire winter, but it is by far the most extreme and prolonged cold-weather torpor documented in any bird, and Hopi tradition had already named the poorwill the sleeping one long before scientists confirmed the behaviour in the 1940s.