Nightjar (Caprimulgus europaeus): Swallow of the night.
I COULDN'T BELIEVE MY FORTUNE WHEN IT HAPPENED. I was hot, sweaty and thoroughly jaundiced at the thought of another afternoon under the relentless, baking sun when I was suddenly thrown a lifeline by the most unlikely of sources: the exhaust note of a 2-stroke moto-cross bike, revving along a back-road neighbouring the breathless oven masquerading as one of Norfolk's pristine heathlands, proved to be my saviour. It was late May when I was surveying an area that I knew nightjars of previous summers had favoured as a breeding locale, although my concentration was beginning to vacillate after a morning's fruitless scouring of every dead leaf of bracken and birch stump. The nightjars should have been here by now -- they usually return to the U.K. during the second week of May, back from the south-eastern depths of the African continent -- but I hadn't (knowingly) laid eyes on one, with my hard-earned knowledge of the bird telling me that I'd almost certainly been walking past them without knowing it, such is the power of their disguise. Then, my moment of fortuity, the 2-stroker triggered off a roosting male hidden somewhere behind a mature stand of gorse, the bird's momentary burst of reeling pitch lasting just long enough for me to pinpoint his hiding place.
Why a fume-belching 2-stroke engine should induce a nightjar into a momentary burst of song is anyone's guess, although the noise reverberating across the heath was certainly monotone, and not dissimilar in complexity (for the out-of-tune human ear) to the nightjar's short burst of noise. To the female nightjar, however, the song is complex, as recent studies have discovered a surprising range of notes (just short of 2,000-per minute) in the male bird's penetrating song, that can last for hours on balmy, sweet summer evenings. Delivered from a favoured perch that is often a dead branch of birch or gorse, the plangent song is almost tropical in accent and carries through the air for a kilometre or more on the stillest nights: at close quarters, the vociferation is intense and quite penetrating as the male bird seemingly changes gear by moving his head from side-to-side, back-and-forth as the unbroken, reeling melody can sound strangely like a cross-over between a slipping fan-belt and forest full of amorous cicadas. Conversely, the disgruntled sounding contact call of the nightjar is an amphibious, toad-like 'kruitch', delivered most often when disturbed or surprised.
Having arrived back from their wintering-grounds, Norfolk's nightjars will return to a favoured heathland of previous seasons, a place offering a mix of open and woody vegetation that includes significant stands of bracken and gorse. After courtship, a simple nest-scrape is made, often next to large pieces of dead wood, with the implicit intent of raising 2-broods of youngsters during the course of the summer. My own observations tell me that the birds prefer to roost and nest with a circular buffer zone (12 - 18-inches) that is clear of vegetation, presumably to give them an unimpeded view of oncoming danger. However, this minor openness of cover does not make them any easier to detect, for the beautifully cryptic, vermiculated plumage of the birds blends perfectly with the shadowy, twisting stems of heather and desiccated bracken. Whilst the animal sits motionless, often parallel to its chosen stump or branch, the keenest of naturalists might scour the immediate area with the utmost fastidiousness, at times looking directly at the creature through binoculars, without the slightest clue to its whereabouts: only the merest squint of the nightjar's black eyes (or the bird's shadow) eventually betrays its camouflage.
The birds that come to breed in Britain are part of the global family of avians known as the Caprimulgidae that covers most of the inhabitable land on Earth, with the exceptions of the very northern and southern tips of the Americas, northern Asia, New Zealand, remote oceanic islands and Antarctica. The family is split into 2 sub-families, the Chordeilinae (nighthawks of the New World) and the Caprimulginae (of which the European nightjar, Caprimulgus europeus, is one) comprising of nearly 70-species in total. To ensure satisfactory viewing of the nightjars, a trip to one of the famous North Norfolk heathlands, Salthouse Heath or Kelling Heath, is strongly advised, dusk being by far the most beneficial period of the day. Calm, balmy evenings will bring the best out of these nocturnal birds, whose rural moniker of bygone years is 'goatsucker', bestowed in the mistaken belief that they milked goats and other livestock with their huge, gaping mouths. This, of course, is not true. The huge gape is evolved to seize night-flying insects, particularly moths, many of which fraternise around the lights of farm sheds where livestock is contained, leading to their erroneous 'goatsucker' tag. On close inspection of the bird's mouth, it is possible to indentify a row of stiff, bristle-like hairs that aid the nightjar in capturing its quarry during the hours of darkness.
Where the swallows, swifts and martins fly and execute their aestival lives during the diurnal hours, the nightjars replicate this ecological niche at night, resembling a fusion between hirrundine and hawk, their flight light and silent, interspersed with glides, dips and hovers as the bird pursues its insect prey. It is not all serenity though; the nightjar has another audible stunt to pull, aside from its churring song, and it's one that can scare the wits out of you should you be taken unawares. If the male bird detects that you (or another male nightjar) are too close to its refuge for comfort, it will fly noiselessly above you, and without warning, clap its wings together on the upstroke, delivering a knee-buckling crack of sound in the still night air, accompanied by a flash of its luminous white wing patches (lacking on the female) in an undertaking designed to distract foes and rivals away from his jealously guarded nesting territory.
If you are struggling to sight the nightjars on a particular patch of heath, you may be able to draw them to your bearing with nothing more than a white handkerchief. Flap it around in the gloaming of the night and you may attract the keen eyes of a resident male, suspicious that his territory is being invaded, mistaking your freshly laundered linen as the wing patches of a rival.
Bright sunlight and an open landscape didn't prevent me from walking straight past this roosting nightjar. Two hours later, on my return journey, the dark shadow resting against the birch stump gave its presence away.
Perched on a cut-off stump amongst prickly gorse bushes, a nightjar keeps a wary eye open for danger hidden amongst the undergrowth. Their superb camouflage makes them incredibly difficult to spot, even with binoculars.
Resting lengthways on a fallen branch of birch, evening sunlight gently illuminates a nightjar's cryptic plumage, delicately offset against the pink heather. Shortly, it will rise from its slumber and set about the nocturnal business of catching moths.