Looking into the whole nightjar issue a bit further, it seems the goat-sucking belief is widespread. The Romans knew the birds as Caprimulgus, meaning 'goatsucker'[1] (also giving rise to its genus, family and order), and the Germans know it as Ziegenmelker, meaning 'billy-goat milker'[2] (the mind boggles!).
It's not just the sucking of the goat that is part of the myth, but also a disease that affects the goat after being suckled. In one version the disease causes blindness [3], and the Rev Gilbert White gave a detailed account of a slightly different version in his
Natural History of Selborne.
The country people have a notion that the fern-owl, or churn-owl, or eve-jarr, which they also call a puckeridge, is very injurous to weaning calves, by inflicting as it strikes at them, the fatal distemper known to cow-leeches by the name of puckeridge. Thus does this harmless ill-fated bird fall under a double imputation which it by no means deserves - in Italy, of sucking the teats of goats, whence it is called caprimulgus; and whith us, of communicating a deadly disorder to cattle. But the truth of the matter is, the malady above-mentioned is occasioned by the Aestrus bovis, a dipterous insect, which lays its eggs along the chines of kine, where the maggots, when hatched, eat their way through the hide of the beast into the flesh, and grow to a very large size.
[4]
These aren't the only myths surrounding nighjars. The bird is also known as the Brain-fever Bird in South Africa, because the insistant churring of its wings is said to be able to drive a camper mad.[5]
In Karl Shuker's
Extraordinary Animals Worldwide there's a quote from Charles Waterton's
Wanderings of a Naturalist in South America:
They are birds of omen and reverential dread. Jumbo, the demon of Africa, and they equally obey the Yabahou, or Demeraran Indian Devil. They are receptacles for departed souls who come back again to earth, unable to rest for crimes done in their fays of nature; or they are expressly sent by Jumbo or Yabahou to haunt cruel or hard-hearted monsters, and retaliate injuries received from them.
[6]
Shuker also suggests the identity of Sri Lanka's mysterious and terror-inducing 'devil bird' is actually one of the island's native nightjars.[7]
Incidentally, the nightjar has even more names than those previously mentioned, including dorhawk and nighthawk.[8]
Sources:
1. Maurice Burton & Robert Burton (eds.) (1976),
Encyclopedia of the Animal Kingdom, p368
2. Kiri Felix (1978),
The Illustrated Encyclopedia of Birds, p207
3. Reader's Digest (1973),
Book of the British Countryside, p308
4. Rev Gilbert White (1789?),
The Natural History of Selborne, p 348
5. Burton & Burton, op. sit
6. Karl Shuker (1991),
Extraordinary Animals Worldwide, p130
7. Ibid. pp133-135
8. Burton & Burton, op. sit