cranes eat river mussels

Cranes are very large birds, often considered the world's tallest flying birds. They range in size from the demoiselle crane, which measures 90 cm (35 in) in length, to the sarus crane, which can be up to 176 cm (69 in), although the heaviest is the red-crowned crane, which can weigh 12 kg (26 lb) prior to migrating. [citation needed] They are long-legged and long-necked birds with streamlined bodies and large, rounded wings. The males and females do not vary in external appearance, but males tend to be slightly larger than females.

The plumage of cranes varies by habitat. Species inhabiting vast, open wetlands tend to have more white in their plumage than do species that inhabit smaller wetlands or forested habitats, which tend to be more grey. These white species are also generally larger. The smaller size and colour of the forest species is thought to help them maintain a less conspicuous profile while nesting; two of these species (the common and sandhill cranes) also daub their feathers with mud which some observers suspect helps them to hide while nesting. [citation needed]