Texas’ wintering whooping crane population did not experience a detectable growth last winter, but the endangered birds did expand into new territories.
The number of whooping cranes wintering on the Texas Coast topped 500 for the third year in a row, according to biologists with the U.S. Fish and Wildlife Service, who completed an analysis of aerial whooping crane surveys.
Dozens of the birds were recorded outside the primary survey area, suggesting an expansion in their winter range, according to a news release from U.S. Fish and Wildlife Service Region 2.
“Next year, we will be adding the Holiday Beach secondary survey area to our primary survey area given we detected enough whooping crane groups there to meet our protocol for inclusion,” said Wade Harrell, U.S. Fish & Wildlife Service’s whooping crane recovery coordinator.
Wade said the cranes’ territory expansion is a natural response to the population’s need for additional habitat.
Depending on available food resources, each pair of whooping cranes needs 300 acres of habitat to spend the winter and raise their young, he said.
“As the population size gradually increases, as it has done for sometime now, they gradually need to find new habitat,” Harrell said. “Most of the expansion occurs in areas of high quality habitat that are adjacent to areas that whoopers already use.”
Holiday Beach, for instance, is adjacent to the Tatton Unit of the Aransas Refuge, he said. But in some cases, biologists have seen the birds expand to new habitats that are farther away from existing, occupied sites.
During the past few years, for example, a few whooping groups have taken refuge in rice agriculture areas in Wharton and Colorado counties, Harrell said.
Whooping cranes have been endangered since 1967 because of habitat loss and over-hunting. The North American population migrates each fall from their breeding grounds in Wood Buffalo National Park in Canada to winter in Texas at the Aransas National Wildlife Refuge and the surrounding area.
All of the whooping cranes alive today, both wild and captive, are descendants of the last remaining 15 cranes that were found wintering at the Aransas National Wildlife Refuge in 1941.
Last winter, preliminary data analysis indicated an estimated 506 whooping cranes, including 39 juveniles, in the primary survey area centered on the Aransas Refuge.
Biologist survey results are comparable with the prior winter’s estimate of 504 whooping cranes, indicating the population remained stable and did not experience detectible population growth. An additional 29 birds were recorded outside the primary survey area during the survey.
The agency attributed the lack of population growth to the low number of chicks fledging in the whooping cranes’ breeding grounds of northern Canada.
As part of an ongoing partnership between the United States and Canadian governments, biologists plan to conduct the next survey in January 2021 and will continue marking whooping cranes with telemetry tracking devices.