Biologists at Aransas National Wildlife Refuge estimate that the number of endangered Whooping Cranes wintering in Texas rose slightly, from 310 last year to 314 this year. The vast majority — 308 cranes — was on the refuge or nearby areas, while an additional six birds were wintering farther afield.
The total does not represent an exact count but rather an estimate based on aerial surveys of more than 153,000 acres of the refuge and surrounding lands. Four years ago, biologists stopped the decades-long practice of attempting to count every Whooper and are now estimating the population based on the so-called distance-sampling survey method. It produces an estimated range of the total population. This winter’s population, according to a three-page summary of the survey, could be as low as 267 birds or as high as 350. The estimate of 308 cranes represents the statistical mid-point of the population range.
Wade Harrell, U.S. Whooping Crane Recovery Coordinator, said severe drought conditions in Texas have eased somewhat, and more cranes spent this winter in coastal marshes — their preferred habitat. In previous years, a couple dozen birds had wintered as far as 150 miles inland.
The winter population survey revealed that more juvenile cranes were in Texas than biologists had expected. Last summer, after the nesting season in Wood Buffalo National Park in northern Canada, researchers predicted that 32 juveniles would migrate south with their parents to winter in Texas. The survey found instead that approximately 39 juveniles were present at Aransas and nearby areas.
“Recruitment of young birds into the adult population is extremely important to the recovery of the species,” Harrell says. “We were thrilled to see preliminary survey numbers included 39 juvenile birds.” — Matt Mendenhall, Managing Editor