Cranes are found on every continent except for South America and Antarctica and inhabit a variety of open habitats, although most species prefer to live near water.
[1] Cranes fly with their necks extended outwards instead of bent into an S-shape (differentiating them from the similar-looking herons)[3] and their long legs outstretched.
[1] The Siberian crane, with an estimated population of 3,500–4,000 mature individuals, is considered critically endangered due to the construction of dams that threaten one of its main wintering grounds.
The species with the smallest estimated population is the whooping crane, which is conservatively thought to number 50–249 mature individuals,[5] and the one with the largest is the sandhill crane, which has an estimated population of 450,000–550,000 mature individuals.
[6] There are currently 15 extant species of crane recognised by the International Ornithologists' Union distributed among four genera.
[7] The cranes are most closely related to the family Aramidae, which contains a single extant species, the limpkin.
[7] Many species of fossil cranes are known from the Eocene onwards; however, their exact number and taxonomy are unsettled due to ongoing discoveries.
The cranes are divided into two subfamilies, which diverged from each other around 31 million years ago: Balearicinae, containing the genus Balearica, and Gruinae, containing the genera Leucogeranus, Antigone, and Grus.