Breeding & Nesting
Whoopers usually build a nest in marshes or shallow ponds, in about 25 cm of water (the flightless chicks can swim to escape predators) and most often in relatively dense stands of bulrush.
A pair usually has two eggs. Both eggs generally hatch, but if both eggs are left in the nest, usually only one chick survives. The reason for this may be related to a food shortage, particularly when wet areas begin to dry out and terrestrial predators, such as the gray wolf, are able to penetrate the cranes' nesting marshes.
The incubation period is 29– 30 days, and both parents share the task of incubating the eggs in the nest. Few eggs are lost to predators thanks, in part, to the vigil of the adult birds. The reddish orange young hatch during the last week in May or the first week in June. From then on, the parents are kept busy feeding their chicks. During the summer, the cranes rarely fly. Some birds may be incapable of flight during short periods due to the molt of major wing feathers.
Family groups frequent the shallows of small ponds and marshes, where the adults perhaps find larval forms of insects such as dragonflies, damselflies, and mayflies, and also snails, small clams, water beetles, leeches, frogs, and small fish to feed their young. When the parent birds kill larger prey, such as snakes, mice, small birds, ducklings, and even birds up to the size of half-grown bitterns, they share the spoils of these hunts with their young.
By the end of September or early October the young birds are ready to try their wings on the 4000 km migration to the Texas winter range. On the way south, the birds spend one to five weeks feeding in their staging (stopover) areas in Saskatchewan. In these areas, undisturbed whoopers may spend the entire one- to five-week staging period on the same quarter or half-section of land. Here the birds fatten up on waste barley and wheat in stubble fields, and roost during the night in nearby wetlands.
http://operationmigration.org/work_wcranes.html
