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CORPUS CHRISTI — Most of the whooping cranes expected to spend winter near Rockport have arrived, but it’s too early to say how many survived the summer and migration from Canada.
At least 98 percent of the world’s only wild migratory flock of the endangered whoopers have arrived in the Coastal Bend, said Wade Harrell, whooping crane recovery coordinator for the U.S. Fish & Wildlife Service.
The birds began their 2,500-mile flight from Wood Buffalo National Park in late summer and the first arrival in the Coastal Bend occurred in mid-October, Harrell said. Most are now scattered along coastal marshes and bays around the Aransas National Wildlife Refuge near Austwell.
Canadian biologists counted 32 new chicks in the fall, each accompanied by two adults. They did not get an exact count of the independent sub adults.
For the second consecutive year, observers have spotted a small group of stragglers at Granger Lake northeast of Austin in Williamson County, Harrell said. Four adults and one juvenile have been counted there, with possibly another adult pair nearby. Five more were seen near El Campo.
This represents an increasingly broader range of habitat for the birds, which is encouraging, Harrell said. It shows the birds’ ability to adapt to changing conditions, while lessening their chances of being wiped out by a cataclysmic event such as a hurricane. Plus it teaches biologists about the whooping crane’s habitat preferences and diet. At Granger Lake the birds eat bugs and aquatic organisms along with waste grains.
“It’s like an insurance policy,” Harrell said. “The more birds were have in more places in Texas the better. Five years ago no one would have thought the birds would have stayed at Granger Lake.”
Last year’s estimate put the population at about 270 birds, divided between the South Texas group and about 15 cranes outside the survey area. By most accounts this is a low estimate, Harrell said.
The actual count is thought to be closer to 300 cranes. And Harrell said he’s expecting about that many, give or take a few. Harrell said this year’s population estimate based on flight surveys around the refuge in November and December should be out by the end of the month.
There’s typically not much fluctuation in the population, he said. Whoopers are slow breeders and don’t reach breeding maturity until they’re 5 years old. Typically they have one chick annually, but it’s not uncommon for a breeding pair to skip a year.
Population estimates on the flock became a controversial issue this past year when the Fish & Wildlife Service changed the way it counts birds in the survey area. Previously and for the past 60 years attempts were made to count each and every bird during thorough aerial counts. During most of this period the flock was much smaller.
The new technique called distance sampling also involves multiple airplane surveys over a broad area, but rather than searching for every individual bird, this technique uses a system of parallel flyovers involving a standardized protocol more easily duplicated by surveyors with varying levels of familiarity with the flock. The method is not designed to produce an exact count but uses a formula to arrive at an reasonable estimate based on a percentage of the population seen during the survey. The formula factors in birds spotted outside the survey area as well as the individual cranes that the system assumes were missed. This is referred to as a peak abundance estimate.Tom Stehn, the former U.S. Fish & Wildlife Service whooping crane coordinator who retired last year after nearly 30 years, said the new method is accurate to within about 15 percent, which he and other whooping crane fans have suggested is an unacceptable error range.
Refuge officials have said the old system no longer is feasible, in part because they don’t have Stehn’s historical knowledge and because habitat issues have caused the birds to move frequently in search of food and water, which remains in short supply.
The refuge began in October preparing habitat for the cranes’ arrival. Since then, workers have burned 6,500 acres to improve feeding areas and expose otherwise hidden food sources. Another 8,000 to 10,000 acres of prescribed burning is planned for the winter, Harrell said.
Degraded habitat became a major issue during the 2009 drought, when an estimated 23 cranes died. The record die-off became the basis of a lawsuit filed by The Aransas Project, a nonprofit group of local governments, advocacy groups and tourism-dependent businesses in the Coastal Bend. The group claims the Texas Commission on Environmental Quality mismanaged water in the Guadalupe River watershed, contributing to the cranes’ deaths.
A ruling in the civil case heard by U.S. District Judge Janis Graham Jack is expected soon.