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 settlers arrived in Nebraska in the 1840s, there have been reports of whooping cranes (Grus americana) observed in that state during their spring and fall migrations. Never as numerous as the sandhill cranes (Grus canadensis), 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 intensive conservation efforts, the population is increasing in size but is experiencing years of ups and downs. Their intrinsic rate of increase gives them the potential to double their population size in 8 years as happened in the 1980’s, however, environmental and anthropogenic factors (including loss of habitat, altered wetland conditions, climate change, and collisions with power lines, among others) cause the population to recover at a much slower rate. The whooping crane is still one of the rarest birds in North America.

The migration route is long (about 2,500 miles) but narrow (about 300 miles wide) and extends through Texas, Oklahoma, Kansas, Nebraska, South Dakota, and North Dakota in the United States, and through Saskatchewan and Alberta in Canada. Some whooping cranes have stopped in Montana and Iowa as well. During fall and spring migrations almost all of the cranes use areas designated as critical habitat including the central part of the Platte River in Nebraska. Since 1975, the Platte River has been considered “the most valuable part” of the whooping crane’s entire migration route. Whooping cranes rest and feed in the wet meadows, sloughs and crop fields along the river and roost in the shallow waters of the river at night. Most whooping cranes in the AWBP make brief stops (one to a few days) on the Platte River before continuing their migration but a few birds have spent more than a month on the Platte, including a few individuals that migrated with flocks of sandhill cranes. Although the Platte is an important stopover for migrating cranes, not all whooping cranes stop in Nebraska in all years. There are other wetlands, small lakes, and ponds along the migration corridor in other states that some cranes use instead of the Platte.

Migration

Interesting facts about whooping crane migration:

• Whooping cranes migrate as individuals, pairs, family groups and small flocks, between 5 to 12 individuals together. However, during the spring migration of 2007 a record number of 34 individual cranes were observed together at Salt Plains National Wildlife Refuge, in Alfalfa County, Oklahoma (probably 4 groups), and during the fall migration of 2007 a record number of 30-35 individuals were sighted in one flock flying above Cherry County in northern Nebraska.
• On occasion, one or two individual whooping cranes will be observed migrating with flocks of sandhill cranes. These cranes tend to stay longer in Nebraska (22 to 33 days).
• Whooping cranes migrate primarily during daylight hours but flights sometimes originate before sunrise and/or continue after sunset. Therefore, cranes can cover a large amount of ground in a long migration day and may never be spotted along the migration path. This explains why the number of sightings reported along the central corridor represents a low proportion of the total number of cranes migrating through the area.
• Radio-tracking of juveniles and subadults in the 1980’s revealed that some cranes can travel over 500 miles in a single flight and approximately 1,140 miles in 2 days.
• Fall migration tends to be longer than spring migration. Fall migration is completed in an average of 29 days. On average, 20.4 of these days are spent in Canada at staging areas in Saskatchewan and Alberta and 8.6 of these days are spent completing the rest of the migration. Spring migration is completed in an average of 18.5 days.

Demography

During the last ten years, recruitment to the whooping crane population has been relatively moderate. Recruitment is affected by young birds being added to the population as well as mortality among adults. The droughts in Texas during the winter of 1999-2000 reduced food resources for the cranes. Numbers of blue crabs at Aransas, a favorite food of whooping cranes, were especially low. In addition, habitat conditions on the breeding grounds during the summer of 2000 were not ideal and 21 of 32 chicks died before the fall migration. This was one of the poorest reproductive efforts in the 40 years for which records exist. The combination of reduced food resources during the winter and poor habitat conditions during the breeding season may be responsible for the population decline in 2000. In 2005, only 3 individuals were added to the total population, but in 2006 and 2007 the increases were higher. The reasons for some 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 two decades ago, only 23 individuals still carried leg bands in 2007. Therefore, we do not know the exact age structure of the current population, so some mortality may be due to natural deaths of older whooping cranes. Currently, 20 banded individuals are older than 20 years old, and one of them is 29 years old!

Platte River in Nebraska

In recent years, whooping cranes have increased their use of habitat that has been restored and is being conserved by The Crane Trust. In 1992, 21 individual cranes were observed on the Platte River, the highest number observed on the Platte since 1942. During 1997, four whooping cranes were observed on the Trust’s property along the Platte River. 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. During the last 10 years the number of individuals using the river has been, on average, 8.3 (+ 4.3). However, 2007 saw a new record being set in the history of whooping crane sightings on the Platte River with 22 total individuals sighted during both migrations (12 in spring, 10 in fall).

Sightings of whooping cranes along the Platte have increased in recent years, likely as a direct result of the increasing number of total cranes in the Aransas-Wood Buffalo population and in part due to the management of the river providing more roosting places for cranes. Since 1941, the Aransas-Wood Buffalo population of whooping cranes has increased from 15 to 266 birds (as of January 2008).