Birds
Crane
Gruidae · also called cranes
A crane announces itself. The call is a bugle produced by a windpipe coiled like a trombone inside the breastbone, and it carries for kilometres across a marsh. Then there is the dance — bowing, leaping two metres straight up, flinging grass in the air — done not just in courtship but year-round, by birds of every age.
Overview
Cranes are the family Gruidae, 15 species on every continent except South America and Antarctica. They are tall, long-necked, long-legged birds of open wetland and grassland, superficially like herons and storks but not closely related to either. They range up to the sarus crane at 1.8 m — the tallest flying bird — and are omnivores, probing for tubers, grain, insects, frogs, and small vertebrates.
The voice
In several species the trachea is over a metre long and loops through a hollow chamber in the keel of the breastbone, working like brass tubing to produce the deep, far-carrying bugle that names the whooping and trumpeter cranes.
Dancing
The full display — bowing, 2 m leaps, wing-running, tossing vegetation — peaks in courtship but is performed all year by all ages and both sexes, apparently to bond pairs, discharge tension, and keep a pair in synchrony for a shared breeding effort.
Long lives, hard journeys
Cranes live 20 to 30 years, breed late, and raise one or two chicks a year. Demoiselle and Eurasian cranes cross the Himalayas at up to 8,000 m, riding rising air through calm-weather windows.
Status
Cranes as a family are Not Evaluated but are one of the most threatened bird families, with a decreasing trend and 11 of 15 species threatened or near threatened. The whooping crane fell to about 15 birds in 1941 and has been rebuilt to a few hundred; the Siberian and red-crowned cranes are Endangered. Wetland drainage, dams, power lines, and poisoning are the main causes.
Crane: common questions
Why do cranes dance?
Dancing is central to how cranes communicate and bond. The full display, bowing, jumping, wing-flapping, running, and throwing vegetation into the air, is most intense during courtship and helps a pair assess and coordinate with each other before breeding. But cranes dance far more widely than that. Chicks dance within days of hatching, unpaired juveniles dance in groups, and established pairs dance through the year. Researchers think it also serves to discharge nervous energy, redirect aggression, and keep a pair in behavioural synchrony, which matters for a bird that shares incubation and defends a large territory. It may simply feel rewarding to the birds as well.
How can cranes fly over the Himalayas?
Demoiselle and Eurasian cranes that breed in Mongolia and Central Asia and winter in India face the mountain wall on each migration. They cross by gaining height on thermals and ridge lift during the day, forming long V-shaped skeins, and pushing through passes and over ridges at 5,000 to 8,000 metres, where the air holds less than half the oxygen at sea level and temperatures are far below freezing. Birds pick clear, calm weather windows, and many still die of exhaustion, cold, or golden eagle attacks during the crossing. Their blood and muscles are adapted to work at low oxygen, and unlike a labouring mammal a flying bird moves air through its lungs very efficiently.
What is the difference between a crane, a heron, and a stork?
They are three separate bird families that share a tall, long-legged, long-necked wading shape through similar lifestyles rather than close kinship. Herons fly with the neck folded back into an S and usually hunt fish by standing still and striking. Storks and cranes both fly with the neck outstretched, but storks are broad-winged soaring birds that often nest on structures and are largely silent, communicating by bill-clattering, while cranes are birds of open marsh and grassland, feed on a wide omnivorous diet by walking and probing, perform elaborate dances, and are among the most vocal of all large birds. Cranes also raise their inner wing feathers into a drooping bustle over the tail, which herons and storks do not.
Why are so many cranes endangered?
Cranes depend on wetlands, and wetlands are among the most heavily altered habitats on Earth, drained for farming, cut off by dams, and drawn down for irrigation and cities. Because cranes are large, breed late, and raise few chicks, they cannot absorb extra losses. On top of habitat loss they collide with power lines, are poisoned deliberately or by treated grain, and are hunted or trapped along migration routes that may cross many countries. Eleven of the fifteen crane species are now threatened or near threatened. The whooping crane, down to about 15 birds in 1941, shows both the danger and that intensive, sustained recovery work can pull a species back.