Cliff pigeons that invented the city sidewalk flock
Rock doves (Columba livia)—common or rock pigeons—are Columbidae birds whose wild form is pale grey with two black wing bars and little male-female difference. They forage on open ground and roost on cliffs; the IOC's official English name is rock dove, ancestor of every street pigeon.
Johann Friedrich Gmelin gave the species its scientific name in 1789 in his expanded edition of Linnaeus's catalogue. Columba traces back to a Greek word for diver, a nod to the bird's swimming motion through the air, while livia derives from Latin for bluish-grey. Gmelin kept no type specimen, so a bird from Fair Isle in Scotland was later chosen to anchor the name. Among its genus-mates the hill pigeon is the closest kin, and nine subspecies stretch from western Europe and North Africa to Sri Lanka.
A wild bird is 30 to 35 centimetres long with a wingspan of 62 to 68, weighing 238 to 380 grams. The head, neck and chest are dark blue-grey with a green-to-purple sheen on the neck, and the best field mark is a white lower back, along with two black bars across pale grey wings and a dark tail band. Females look almost the same but with a duller sheen. In flight the white underwing shows, and the bird glides with wings raised in a steep V. Its call is a soft, wavering coo, and display involves a puffed throat, fanned tail, strutting and bowing.
Originally a cliff-nester of southern Europe, North Africa and western Asia, it foraged on open ground. Domestication produced around a thousand breeds in red, brown, chequered and pied forms, and escapees founded feral flocks worldwide; counting them, there may be 17 to 28 million in Europe and up to 120 million globally. Pure wild birds are now endangered in many places, surviving best in northern and western Scotland, especially the Outer Hebrides.
Rock doves manage water with their kidneys rather than salt glands, excreting nitrogen as uric acid, which saves water but costs energy. Their long flight range lets desert birds reach distant water, and their eggshells carry pores that regulate moisture loss as embryos develop.
Source: Rock dove
