Nightjar nonsense

At evening, when most birds are snug in their roosts, nightjars around the world are stirring, readying themselves to make the lives of nocturnal insects that little bit more difficult. Their agile flight and huge, gaping mouths help them catch many a moth and beetle on the wing, but it was once widely believed that they fed by latching onto the teats of goats to drink their milk – hence their other name of “goatsucker” and their family name Caprimulgidae. Naturalists now know better, of course, but one in our hall of fame may have helped replace this myth with another. The idea that nightjars steal goats' milk stems from antiquity. Volume XVI of the Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge (1840; London, UK: Charles Knight and Co) beautifully records the words of Pliny the Elder, in his 1st-century AD work, Natural History: “They enter the folds, and fly to the udders of the goats in order to suck the milk, from which injury the udder dies away, and blindness falls upon the goats which have been so sucked”. It also quotes from Aristotle's 4th-century BC work, History of Animals: “Flying upon the goat, it sucks them, whence it has its name. They say that when it has sucked the teat it becomes dry, and that the goat becomes blind”. True to the Society's name and mission, the tome also provides the useful knowledge that this is, of course, absurd. Waiting for a goat to go by? Perhaps this belief was inspired by the nightjar's cavernous maw, into which a goat teat might seem to readily fit. Perhaps flocks of goats returning to their evening shelter sometimes disturbed the waking birds, which commonly sit on the ground, and thus an association between them was established. But one explanation of how the myth originated eventually gained, and still enjoys, consensus: nightjars approach domestic animals not to take their milk, but to gobble up their insect entourage (see for example DT Holyoak's Nightjars and Their Allies: The Caprimulgiformes [2001; New York, NY: Oxford University Press]). The respected 19th-century naturalist Charles Waterton lent weight to this idea by reporting nightjars feeding directly on livestock. In his book Wanderings in South America (1839; London, UK: B Fellowes), which contains descriptions of Guyana's wildlife during the early 1800s, the following appears: When the moon shines bright you may have a fair opportunity of examining the goatsucker. You will see it close by the cows, goats, and sheep, jumping up every now and then under their bellies. Approach a little nearer…See how the nocturnal flies are tormenting the herd, and with what dexterity he springs up and catches them, as fast as they alight on the belly, legs, and udder of the animals. Observe how quiet they stand, and how sensible they seem of his good offices, for they neither strike at him, nor hit him with their tail, nor tread on him, nor try to drive him away. There is much to admire in Waterton's writings, but I have seen many, many nightjars in Africa, plus a few in Spain, and never once did they behave like nocturnal oxpeckers! Might Waterton have spun his own myth? “I've never seen nightjars feeding directly on livestock either”, says Ruben Evens, a nightjar researcher at Hasselt University (Diepenbeek, Belgium), with some 15 years' experience observing these birds in Europe and Africa. “In my experience, nightjars prefer to feed in meadows where extensive grazing of livestock takes place. Lots of insects breed and grow in livestock droppings, which means food for nightjars. But do they feed directly on livestock? I don't think so.” “I have never seen a nightjar forage directly on livestock, or even close to them”, adds Mark Brigham (University of Regina, Canada), who has studied many a caprimulgid. “I have no knowledge of my students or colleagues seeing this either.” Nightjar specialist and author Des Jackson (Toowoomba, Australia) recalls an observation of a fiery-necked nightjar (Caprimulgus pectoralis) apparently taking insects flushed out by a man walking his dog (Ostrich 1988; 59: 38–39). But he too admits: “I don't know of any nightjar that alights on a beast to take prey.” And neither does Brian O'Shea, Collections Manager for Ornithology at the North Carolina Museum of Natural Sciences (Raleigh, NC), who has observed nightjars in Waterton's Guyana. “Nightjars take their prey in mid-air by sallying from either a perch or the ground. It's possible that they sometimes follow livestock to feed on insects disturbed by them, but neither I nor anyone I know has ever observed them picking insects directly from the animals, and I don't imagine they would do so.” So what was Waterton's goatsucker? Who knows? Maybe it's now extinct. Maybe he misidentified his bird. One thing, however, is certain: not even he saw one hanging from a goat's teat!

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