The largest migrating flock of whooping cranes in the wild is set to return to Texas in record numbers over the next few weeks.

State and federal wildlife officials say they expect as many as 290 cranes to make the trip from their nesting grounds in Canada — an extraordinary comeback two years after the deadliest winter on record for the critically endangered bird.

"Right now everything is looking really good," said Tom Stehn, whooping crane coordinator for the U.S. Fish and Wildlife Service.

The chief reason, Stehn said, is water. The cranes had plenty of it in Canada's Wood Buffalo National Park, where they breed, and should find what they need for survival while wintering near Corpus Christi.

"It's no secret," Stehn said. "If you want whooping cranes to do well, just add water."

A far grimmer mood gripped the Aransas National Wildlife Refuge over the last two years because of food and water shortages.

A record 270 whooping cranes arrived at Aransas two years ago, but 23 birds died of starvation or other related problems.

Wildlife biologists blamed the die-off on a dry spell that reduced the Guadalupe River's flow so severely that the supply of fresh water and food dwindled in the San Antonio and Aransas Bay system.

Two already in Aransas

The cranes feast on blue crabs in the coastal marshes for protein, but the crabs need a certain amount of fresh water to live, and the river's low flow made it too salty for them.

What's more, the cranes, already weak from a lack of food, had farther to fly for drinking water.

The scientists predicted another tragic winter for the iconic bird last year.

But rains broke the two-year drought during the cranes' stay, and the flock remained all but intact - one died in Texas - before making the 2,400-mile trip north for the summer.

In Canada, the flock grew by 46 chicks, the second-highest number on record, prompting Stehn's estimate of a record return to Texas. The first two cranes arrived at Aransas last week, and all of them should be there by Christmas.

The long-necked cranes, protected by the Endangered Species Act, are white with black wingtips and crimson crowns. They typically stand about five feet and can have a wingspan of seven and a half feet.

Despite the upbeat forecast for the cranes' stay in Texas, environmentalists remain concerned about the long-term health of the species because of the area's already stressed water supply.

The Aransas Project, an alliance of local governments and conservation groups, filed suit earlier this year against state regulators to ensure enough fresh water reaches the bay, especially during dry times. The case is set for trial in March before a federal judge in Corpus Christi.

Water still critical factor

Jim Blackburn, a Houston-based attorney representing the group, said the flock's improving numbers reinforce the idea of a dedicated flow of fresh water for the Guadalupe basin.

"There are blue crabs in the marsh (for the cranes to eat), but we've had rain," Blackburn said. "That's how these things work. As long as there is plentiful water, everything is fine."

The Texas Commission on Environmental Quality, which governs rights to the state's fresh water, declined to comment, citing pending litigation.

matthew.tresaugue@chron.com