The European nightjar (Caprimulgus europaeus), common goatsucker, Eurasian nightjar or just nightjar is a crepuscular and nocturnal bird in the nightjar family that breeds across most of Europe and the Palearctic to Mongolia and Northwestern China. The Latin generic name refers to the old myth that the nocturnal nightjar suckled from goats, causing them to cease to give milk. The six subspecies differ clinally, the birds becoming smaller and paler towards the east of the range. All populations are migratory, wintering in sub-Saharan Africa. Their densely patterned grey and brown plumage makes individuals difficult to see in the daytime when they rest on the ground or perch motionless along a branch, although the male shows white patches in the wings and tail as he flies at night.
The preferred habitat is dry, open country with some trees and small bushes, such as heaths, forest clearings or newly planted woodland. The male European nightjar occupies a territory in spring and advertises his presence with a distinctive sustained churring trill from a perch. He patrols his territory with wings held in a V and tail fanned, chasing intruders while wing-clapping and calling. Wing clapping also occurs when the male chases the female in a spiralling display flight. The European nightjar does not build a nest, and its two grey and brown blotched eggs are laid directly on the ground; they hatch after about 17–21 days and the downy chicks fledge in another 16–17 days.
The European nightjar feeds on a wide variety of flying insects, which it seizes in flight, often fly-catching from a perch. It hunts by sight, silhouetting its prey against the night sky. Its eyes are relatively large, each with a reflective layer, which improves night vision. It appears not to rely on its hearing to find insects and does not echolocate. Drinking and bathing take place during flight. Although it suffers a degree of predation and parasitism, the main threats to the species are habitat loss, disturbance and a reduction of its insect prey through pesticide use. Despite population decreases, its large numbers and huge breeding range mean that it is classified by the International Union for Conservation of Nature as being of least concern.
Taxonomy
The European nightjar was described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae under its current scientific name. Caprimulgus is derived from the Latin capra, "nanny goat", and mulgere, "to milk", referring to an old myth that nightjars suck milk from goats, and the species name, europaeus is Latin for "European". The common name "nightjar", first recorded in 1630, refers to the nocturnal habits of the bird, the second part of the name deriving from the distinctive churring song. Old or local names refer to the song, "churn owl", habitat, "fern owl", or diet, "dor hawk" and "moth hawk".
The nightjars, Caprimulgidae, is a large family of mostly nocturnal insect-eating birds. The largest and most widespread genus is Caprimulgus, characterised by stiff bristles around the mouth, long pointed wings, a comb-like middle claw and patterned plumage. Adult males, and sometimes females, have white markings in the wing and tail, shown to serve as male quality indicators. Within the genus, the European nightjar forms a superspecies with the rufous-cheeked nightjar and the sombre nightjar, African species with similar songs.
Subspecies
There are six recognised subspecies, although the differences are mainly clinal; birds become smaller and paler in the east of the range and the males have larger white wing spots. Birds of intermediate appearance occur where the subspecies' ranges overlap. The adult of the nominate subspecies has greyish-brown upperparts with dark streaking, a pale buff hindneck collar and a white moustachial line. The closed wing is grey with buff spotting, and the underparts are greyish-brown, with brown barring and buff spots. The bill is blackish, the iris is dark brown and the legs and feet are brown. Given their nocturnal habits, cryptic plumage and difficulty of observation, nightjar observation "is as much a matter of fortune as effort or knowledge". Even a singing male may be hard to locate; the perched bird is difficult to spot in low light conditions, and the song has a ventriloquial quality as the singer turns his head.
Despite the name, wing-clapping does not involve contact between the two wing tips over the bird's back as was once thought. The sound is produced in a whiplash-like way as each wing cracks down.
Distribution and habitat
thumb|[[Heathland is a favoured habitat.]]
The breeding range of the European nightjar comprises Europe north to around latitude 64°N and Asia north to about 60°N and east to Lake Baikal and eastern Mongolia. The southern limits are northwestern Africa, Iraq, Iran and the northwestern Himalayas.
All populations are migratory, and most birds winter in Africa south of the Sahara, with just a few records from Pakistan, Morocco and Israel. Migration is mainly at night, singly or in loose groups of up to twenty birds. European breeders cross the Mediterranean and North Africa, whereas eastern populations move through the Middle East and East Africa.
Most birds winter in eastern or southeastern Africa, Vagrants have occurred in Iceland, the Faroe Islands, the Seychelles, They have a unique serrated comb-like structure on the middle claw, which is used to preen and perhaps to remove parasites. notably the common poorwill, which will maintain that state for weeks. The European nightjar has been observed in captivity to be able to maintain a state of torpor for at least eight days without harm, but the relevance of this to wild birds is unknown.
Breeding
right|thumb|A clutch of two eggs on the ground in Turkey
thumb|Egg, Collection [[Museum Wiesbaden]]
Breeding is normally from late May to August, but may be significantly earlier in northwest Africa or western Pakistan. Returning males arrive about two weeks before the females and establish territories which they patrol with wings held in a V-shape and tail fanned, chasing intruders while wing-clapping and calling. Fights may take place in flight or on the ground. The male's display flight involves a similar wing and tail position with frequent wing clapping as he follows the female in a rising spiral. If she lands, he continues to display with bobbing and fluttering until the female spreads her wings and tail for copulation. Mating occasionally takes place on a raised perch instead of the ground. In good habitat, there may be 20 pairs per square kilometre (50 per square mile).
Several nightjar species are known to be more likely to lay in the two weeks before the full moon than the during the waning moon, possibly because insect food may be easier to catch as the moon waxes. A study specifically looking at the European nightjar showed that the phase of the moon is a factor for birds laying in June, but not for earlier breeders. This strategy means that a second brood in July would also have a favourable lunar aspect.
thumb|Adults with chicks from Saudi Arabia
Eggs are laid 36–48 hours apart, and incubation, mainly by the female, starts with the first egg. The male may incubate for short periods, especially around dawn or dusk, but spends the day roosting, sometimes outside his territory or close to other males. If the female is disturbed while breeding, she runs or flutters along the ground feigning injury until she has drawn the intruder away. She may also move the eggs a short distance with her bill. Each egg hatches after about 17–21 days. The semi-precocial downy chicks are mobile when hatched, but are brooded to keep them warm. They fledge in 16–17 days and become independent of the adults around 32 days after hatching. A second brood may be raised by early nesting pairs, in which case the female leaves the first brood a few days before they fledge; the male then cares for the first brood and assists with the second. Both adults feed the young with balls of insects which are either regurgitated into the chick's mouth or pecked by the chick from the adult's open bill. European nightjars breed when aged one year, and typically live four years. The adult annual survival rate is 70%, but that for juveniles is unknown. The maximum known age in the wild is just over 12 years. It will pick glowworms off vegetation. It consumes grit to aid with digesting its prey, but any plant material and non-flying invertebrates consumed are taken inadvertently while hunting other food items. Young chicks have been known to eat their own faeces. Migrating birds live off their fat reserves. They have long sensitive bristles around the mouth, which may help to locate or funnel prey into the mouth.
Nightjars have relatively large eyes, each with a tapetum lucidum (reflective layer behind the retina) that makes the eyes shine in torchlight and improves light detection at dusk, dawn and in moonlight.
Predators and parasites
The eggs and chicks of this ground-nesting bird are vulnerable to predation by red foxes, pine martens, European hedgehogs, european badgers, least weasels and domestic dogs, and by birds including crows, Eurasian magpies, Eurasian jays and owls.
In Britain and elsewhere, commercial forestry has created new habitat which has increased numbers, but these gains are likely to be temporary as the woodland develops and becomes unsuitable for nightjars.
In culture
thumb|"Nightjar, goatsucker, or fern-owl", alternative old names, by [[J.G. Keulemans]]
Poets sometimes use the nightjar as an indicator of warm summer nights, the latter actually caused by botfly larvae under the skin. "Lich fowl" (corpse bird) is an old name which reflects the superstitions that surrounded this strange nocturnal bird. Like "gabble ratchet" (corpse hound), it may refer to the belief that the souls of unbaptised children were doomed to wander in nightjar form until Judgement Day.