The whooping crane, a migratory species that traversed between sites in the US and Western Canada, had all but died out by the mid-1940s, with just 21 birds remaining. Habitat loss and indiscriminate hunting had just about done it in. Hunting the birds had been banned for over 20 years by then, but recovery from such small numbers was not guaranteed.
In the 1960s biologists embarked on a captive breeding programme to boost numbers. This involved getting the monogamous birds to produce more than one clutch of eggs every breeding season, by taking away the first eggs laid for artificial incubation, encouraging the couple to mate again and lay more. Chicks born from eggs left in the nest were raised by the adult birds, but those hatched in an incubator imprinted with their human keepers. In order to make these birds capable of being released in the wild, keepers dressed head to toe in white crane costumes and taught the hatchlings whooping crane behaviour.
