A record number of 164 whooping cranes are currently incubating their eggs in the 82 nest counted recently by the Canadian Wildlife Service in its annual survey. These endangered birds all nest in and around Wood Buffalo National Park (WBNP), Canada. According to the U.S. Fish and Wildlife Service an estimated 300 whooping cranes migrated to Canada from their winter habitat on Aransas Refuge, Texas. Friends of the Wild Whoopers (FOTWW) consider, based on this information that it is likely that over 50 percent of these wild whoopers are involved with nesting.
This year, the 82 whooping crane nests counted on Wood Buffalo is an increase from 74 discovered this time last year. This number surpasses a previous record of 76 nests, set after a survey conducted in spring 2011.
So what is currently going on in the nesting area? Most likely the whoopers had laid their all their eggs before the nest survey was completed. Research on whooping cranes nesting has been conducted over many years and unlocked some of the giant bird’s secrets. FOTWW has reviewed some of the research and summarized it here for you.
Whoopers normally lay their eggs in late April to mid-May, and hatching occurs about 1 month later. Based on past research, approximately 90% of the nest will contain 2 eggs, 9% will contain 1 egg and 1% will contain 3 eggs. Eggs average 100 mm in length and 63 mm in width. Whooping crane pairs share in incubation of the eggs. Incubation lasts from 29 to 31 days.
Incubation ends when the light brown eggs hatch. Whooping cranes may re-nest if their first clutch is destroyed or lost before mid-incubation. Fortunately, egg predation is uncommon, and re-nesting by whooping cranes is believed to be rare.
So, normally whooping cranes usually produce clutches of 2 eggs laid 48 to 60 hours apart. Incubation begins with the first egg laid. Therefore, hatching of the eggs does not occur at the same time. Normally the first chick hatched is one or two days old before than the second is hatched. According to some research, eggs laid after incubation has begun (the 2nd egg) usually only produce fledged young if the earlier laid egg fails to hatch or the chick dies soon after hatching.
While whooping cranes may lay 2 eggs, only about 10% of whooper pairs migrating back to their Texas winter range have 2 chicks. About 90% of nests therefore contain 1 egg that is unlikely to result in a fledged chick. Still, the second egg plays a possible role in providing assurance that at least one chick survives. In nests with 2 eggs, the first hatched has the greater chance of survival in the wild because the parents can provide better care to a single chick.
Except for brief intervals, one of the parents normally remains on the nest at all times. Chicks are capable of swimming shortly after hatching; however, parents and young return to the nest each night during the first 3 to 4 days after hatching. Later, parents brood their young wherever they are at night or during foul weather. During the first 3 week after hatching, whooping crane families generally remain within about one mile of the nest site.
Whooping cranes are good parents and find food for their chicks, protect them from predators and teach them the migration route between Wood Buffalo National Park and Aransas National Wildlife Refuge.
Likely some of the whooper chicks have already hatched and others will soon. FOTWW is hopeful for a record number of chicks following the record number of nests. Canadian Wildlife Service personnel will soon be taking to the skies to count the chicks.
***** FOTWW’s mission is to protect the Aransas/Wood Buffalo population
of wild whooping cranes and their habitat. *****