Cranes are a clade (Gruidae) of large, long-legged and long-necked birds in the group Gruiformes. There are fifteen species of crane in four genera. Unlike the similar-looking but unrelated herons, cranes fly with necks outstretched, not pulled back. Cranes live on all continents except Antarctica and South America. Most species of cranes are at the least classified as threatened, if not critically endangered, within their range. The plight of the Whooping Cranes of North America inspired some of the first US legislation to protect endangered species. They are opportunistic feeders that change their diet according to the season and their own nutrient requirements. They eat a range of items from suitably sized small rodents, fish, amphibians, and insects, to grain, berries, and plants. Most have elaborate and noisy courting displays or 'dances'.