Aransas-Wood Buffalo Population (AWBP) modeling study. 2007 Whooping Crane Recovery Team Meeting Presentation by Dr. K. Gil-Weir. Current Visiting Researcher at the Platte River Whooping Crane Maintenance Trust (PPT file - Must use Internet Explorer 6 or newer to view).

THE WHOOPING CRANE is not only the tallest bird in North America—it is one of our most spectacular and recognizable symbols for the conservation of endangered species. Since white settlers arrived in Nebraska in the 1840s, there have been reports that whooping cranes (Grus americana) were observed here during their spring and fall migrations. Never as numerous as the sandhill cranes, the whooping crane reached the very brink of extinction earlier in this century—only 15 birds remained in the population in 1941. After years of intense conservation efforts, the population is increasing in size, but the whooping crane still is one of the rarest birds in North America.

Whooping cranes spend the winter along the Gulf coast of Texas, at Aransas National Wildlife Refuge, and each spring they migrate to their nesting grounds in northern Canada, at Wood Buffalo National Park. The migration route is long but narrow, and the birds pass right over the central part of the Platte River. The Platte provides stopover habitat along the migration route that is critically important to the population. Whoopers rest and feed in the wet meadows and sloughs and crop fields along the river, and at night they sleep roosting in the shallow waters of the Platte. Most whooping cranes make brief stops on the Platte River before continuing their migration (one to a few days), but in some years individual birds have spent more than a month here on the Platte.

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Number of Adults 167 Number of Young 28 Total Number of Birds    195 Number of Nests in 2003 61 Number of Chicks Hatched 45 Change in Size of Population from Last Year +11 Date of Most Recent Update 9/2003

Annual recruitment and population increases may depend on weather conditions during the nesting season and the migration periods. During 1997, for example, wet conditions on the nesting grounds produced high water levels in the shallow lakes where the whoopers nest. High water maintained secure nest sites, which resulted in a record large number of nests (49) and chicks (58) in 1997. However, whooping cranes are very vulnerable during the first year of life, and migration is a hazardous business. Each year, many of the chicks hatched in the summer are lost by the time the flock arrives at Aransas for the winter.

During the last few years, recruitment to the whooping crane population has been relatively poor. Recruitment is affected by young birds being added to the population as well as mortality among adults. The reasons for recent losses of adult birds are not entirely known. The rigors of migration and habitat conditions may be contributing factors, as well as the current age structure of the population. Because banding of chicks ceased a decade ago, it is now impossible to know the exact age structure of the population, but some mortality may be due to natural deaths of old whooping cranes. The drought in Texas during the winter of 1999-2000 also reduced food resources for the cranes. Numbers of blue crabs, a favorite food of whooping cranes, were especially low. In addition, habitat conditions on the nesting grounds during summer 2000 were not ideal, and 21 of 32 chicks died before the southward migration. This is one of the poorest reproductive efforts in the 63 years for which records exist. The combination of reduced food resources during the winter and relatively poor habitat conditions during the nesting season may be responsible for the population decline in 2000.

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In recent years, whooping cranes have made increasing use of habitat that is conserved and has been restored by the Platte River Trust. During 1997, four whoopers were observed on the Trust’s property along the Platte. In 1998, an individual whooping crane stayed in this area for more than a month and roosted for most of that time in the river adjacent to two areas protected by the Trust.

Sightings of whooping cranes along the Platte have increased recently, probably a direct result of the increasing number of birds in the population. Since 1941, the Aransas-Wood Buffalo population of whooping cranes has increased from 15 to 198 birds (as of August 2003).

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