The whooping crane is the largest North American bird, reaching an average of 5 feet (1.5 m) in height. It has a large wingspan of up to 8 feet (2.5 m). This endangered species is omnivorous, eating shellfish, fruit, invertebrates, insects, nuts and plant matter.
Quite similar in appearance to the sandhill crane, these tall birds have predominantly white plumage with black wing tips and red cheek patches, with an additional patch running over the top of the head. Young whooping cranes have pale, reddish-brown and white plumage until they reach maturity and gain their adult plumage, including the red patches. Juveniles are unusual in that they are born with blue eyes that gradually turn yellow as they mature.
Between 1941 and 1942, the whooping crane was reduced to a tiny population of a mere 16 birds. The whooping crane had been brought to the brink of extinction because of a variety of factors that included recreational shooting, egg collecting, human expansion and the extensive loss of their wetland habitats. Another influence on the decline in numbers is that whooping cranes do not reach sexual maturity until they are 5 years old. This slow sexual maturation meant that so few birds were born each year that the population could not recover enough to make up for the number of birds being killed.
Female whooping cranes lay one or two eggs per season, from two to three days apart. Usually only the older offspring survives, because the second chick is smaller and weaker and is often trampled or thrown out of the nest by the older sibling. Whooping cranes nest in open marsh and wetlands in shallow depressions lined with vegetation in shallow water. Both parents incubate the eggs and raise the chicks. Whooping cranes mate for life but still participate in regular courtship rituals with their life partners.
There is only one natural population of whooping cranes left, estimated to include between 165 and 200 birds. They spend the cold winter months in Texas, at Aransas National Wildlife Park, and the spring and summer breeding season at Wood Buffalo National Park in Canada. Fossil deposits date the presence of whooping cranes back to more than 2 million years ago and covering a much larger geographic range.
A small, non-migratory flock has been introduced from captive-bred birds that live all year on Florida's Kissimmee Prairie; additional reintroductions are planned with a long-term view to re-establish the whooping crane and increase its numbers to a self-sustaining level. There have been many unsuccessful reintroduction attempts since the 1960s, including putting viable whooping crane eggs in the nests of breeding sandhill cranes. Most of these eggs hatched and were raised by the sandhills. These offspring had an exceptionally high mortality rate and would only breed with sandhill cranes, not their own species. The reasons for this remain unclear.