Nonprofit starts its own count of whoopers
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For the Aransas-Wood Buffalo whooping crane population to be considered for down-listing under the Endangered Species Act, the flock must reach at least 1,000 individual birds and 250 reproductive pairs, according to the U.S. Fish and Wildlife Services.
Researchers with the International Crane Foundation say the U.S. Fish and Wildlife Service's survey of whooping cranes is missing valuable information and have started their own count of the endangered birds.
Historically, the U.S. Fish and Wildlife Service's census begins in November, when the birds arrive in the Aransas National Wildlife Refuge and continues almost every week until April, when the birds migrate north to nest in Canada's Wood Buffalo National Park, said Liz Smith, a conservation biologist with the foundation.
She said the new Fish and Wildlife Service surveys are concentrated in one month, but the birds' diet and behavior changes during their six-month stay at the Texas refuge.
"All stages of the wintering food dynamics can have an impact on the birds. If they have not been able to eat enough, the chances of them having a successful breeding season are lower," Smith said.
She said that to gain more information about the ecology of whooping cranes, the foundation has teamed up with tour boat Capt. Tommy Moore, of Rockport, for the third year to conduct counts of the cranes about once a week, depending on the weather.
Moore said the counts are conducted along 10 miles of shoreline up the Intracoastal Waterway on the east side of Blackjack Peninsula.
Smith said the foundation's counts are not censuses and are not comparable to the wildlife service counts but generate some of the information lost when the wildlife service switched to the new method. The counts cover about 20 percent of the cranes' wintering habitat, Moore said.
"We will be able to see how a subset is doing and how they are reacting to freshwater inflow," Smith said.
For 61 years, the U.S. Fish and Wildlife Service conducted a census of the whooping cranes while they wintered in Aransas National Wildlife Refuge, said Tom Stehn, retired whooping crane coordinator for the wildlife service.
Stehn said he counted the birds at least eight times during the wintering season, and if weather and the budget permitted, he would fly almost every week.
"But now, they are just doing a very limited number of flights. They have no way of knowing if a bird dies in February because they aren't flying in February or March," Stehn said.
The new method, adopted in 2011, requires observers to count the birds six times during a wintering season, said Wade Harrell, whooping crane coordinator for the wildlife service. In 2012, the wildlife service personnel conducted seven surveys of the primary wintering grounds in December, according to a February 2013 Whooping Crane Update issued by the wildlife service.
The 2011 change was an agency decision, Harrell said.
He said more whooping cranes wintering in an expanded whooping crane habitat affected the decision to switch to a survey method instead of a census. Surveys count a percentage of the population and use a mathematical calculation to account for the rest while a census is an attempt to count an entire population.
Smith said the wildlife service's new surveys are concentrated in December, when the peak number of birds are in the Aransas National Wildlife Refuge, and are capable of estimating the size of the flock when the birds arrive in the refuge but do little to help understand the birds' well-being throughout their winter stay at the refuge.
"Without doing the weekly surveys, we don't know the mortality in the wintering ground," Smith said.
Smith said the tides are high when the whooping cranes arrive in the coastal marshes from their 2,600-mile migration south, and the birds fill up on a high-protein diet of blue crabs. The tides go down in late December, she said, and the birds' begin eating more wolfberries, which ripen in late December and early January. The little red berries, which look like Hot Tamales candies, are easy to pick and highly nutritious, Smith said.
She said when the wolfberry fruit season ends and the tide lowers further, the cranes' diet switches to crabs and clams. Then in March, the ponds in the coastal marshes fill back up with water as the tide rises, and the birds load up on blue crabs before taking off for Canada.
Smith said efforts to understand and repair whooping cranes' ecology double as efforts to understand and repair the coastal ecosystem.
"The whooping crane is like a barometer for how well we are doing. When they aren't doing well, the ecosystem isn't doing well, either. We depend on the ecosystem for economics," Smith said.
She said the foundation has conducted 10 to 15 counts the past two years and is stepping up its efforts to conduct counts this year because conditions for the whooping cranes seem to be improving.
"We just went through two years of probably the worst drought. We haven't recovered yet from that drought. But the rain we have received in the local area has lowered the salinity somewhat in the bay," Smith said.
She said higher levels of salinity lead to lower levels of food like blue crabs, which are necessary for the whooping crane to survive. A big concern with this species is there is one wintering area and one breeding area, Smith said.
"It isn't something that we can hope will recover on its own," she said. "There isn't another place for them to move to."