Standard-winged Nightjar

During the breeding season, the male grows one of the flight feathers on each wing, the second primary, into a dramatically elongated structure, in which most of the feather is reduced to a long, bare, wire-like central shaft, and only the far tip carries a broad expanse of feathering that forms a flag, pennant, or standard, which is where the bird gets its name. These modified feathers can each project around 38 centimetres beyond the wing, so a displaying male in flight appears to be trailing two enormous ribbons, each nearly twice the length of his own body, an appearance so unusual that early observers sometimes mistook the flags for small birds flying alongside the nightjar.

No. The elongated wing feathers are a purely seasonal, breeding-only feature. The male grows them as the breeding season approaches, uses them exclusively in courtship display flights over a period of weeks or months, and then moults them out once breeding is finished, after which he looks essentially identical to a female or to a non-breeding male, that is, like a fairly typical, cryptically patterned nightjar. This is an expensive strategy, since growing and repeatedly regrowing such large feathers, and flying with the aerodynamic burden they impose, both cost energy, which is part of why the plumes are considered an honest signal of a male's fitness.

A displaying male performs slow, buoyant flight around one or more females, often near the ground, with the two flag-tipped shafts streaming behind and curving up above his body so that the feathered flags flutter conspicuously in the air. The overall effect is a slow-motion aerial display that draws the female's attention to the size, symmetry, and condition of the plumes, and because only a male in good physical condition can grow full, undamaged standards and fly well while carrying them, females are thought to use the display as a way of assessing which males would make the best mates.

For most of the year the standard-winged nightjar has no long feathers at all and relies, like all nightjars, on outstanding camouflage, its mottled grey-brown plumage making a motionless bird almost impossible to see against bare earth or leaf litter during the day. Even during the breeding season, the male carries the elongated plumes only in flight and while displaying, and he still roosts by day in the same cryptic, frozen posture. The plumes do make displaying males more conspicuous and slightly less agile, which is a real cost, but this risk is confined to a limited period and is offset by the reproductive advantage a successful display provides.