Foster-Rearing Program for Whooping Cranes Beset by Problems : Ecology: Power lines, avian tuberculosis, drought and females uninterested in mating have plagued the effort, which was suspended this year. Only 13 birds remain in the New Mexico flock.

BOSQUE DEL APACHE, N.M. —  The stately, snow-white bird stands head and shoulders above its gray cousins searching for grain among the frost-tipped stubble of the dark gold New Mexico field.

The “whooper” is alone in the sea of sandhill cranes but the smaller birds give the adopted flock member room and respect.

The uncommon sight of an endangered whooping crane in the wetlands of the middle Rio Grande Valley in New Mexico has become yet more rare in the last few years.

It could be gone forever by 1992 if officials end the unusual foster-rearing program that started the New Mexico flock, a program beset by a number of problems, especially that of breeding.

“We don’t know which way it’s going to go,” said Rod Drewien, the head of the 14-year-old U.S.-Canadian project that takes eggs from the only existing wild whooping crane flock and places them with sandhill crane foster parents. “Beyond 1991, I don’t view it one way or another.”

Drewien is one of the optimists.

The flock, raised by sandhills that nest at Grays Lake National Wildlife Refuge in southeastern Idaho, once numbered 34 birds. Just 13 successfully completed this fall’s 800-mile migration to Bosque del Apache National Wildlife Refuge in central New Mexico, winter home to some 20,000 sandhill cranes.

For the first time this spring, the American and Canadian whooping crane recovery teams suspended placement of eggs with the sand-hills. They recommended the program be re-evaluated in two years and discontinued if breeding remains a problem.

Scientists were encouraged in the first few years of the program but the enthusiasm began to falter as the whoopers reached breeding age and it was discovered that the females were not interested in mating. This made it impossible for the fledgling flock to sustain itself.

“We don’t think the males are the problem. We’re more concerned the females are improperly imprinted (with sexual behavior),” said Jim Lewis, national whooping crane coordinator for the U.S. Fish and Wildlife Service.

The females migrate with the males to Bosque del Apache in the fall but spread out when they return north for the summer, leaving the males alone at Grays Lake when the breeding season starts.

Males also greatly outnumber females, which, for unknown reasons, have a harder time surviving under sandhill care, even in captivity, Lewis said.

“It may be because the (young) males are stronger and bigger and the sandhills aren’t nurturing the young birds long enough,” he said.

Drewien said the breeding problem should have been addressed earlier.

“It was apparent early on that the females weren’t coming back but we did not actively intervene. When we got around to discussing it, we got hit with other problems,” he said.

Like a five-year drought in Idaho.

Of 288 eggs placed with the sandhills at a cost of $2 million, just 85 birds have survived to flight age. Drewien said just one of the 13 remaining birds was hatched after 1985. The rest were hatched before the drought started, making the young birds more accessible to predators.

And weather was not the only unforeseen hardship.

“When we started this, we couldn’t predict we’d lose a bunch of birds to power lines. We couldn’t predict we’d lose birds to avian tuberculosis,” Drewien said.

Power lines have taken a particularly high toll during migration through the San Luis Valley of Colorado, an area Drewien called “the black hole for this flock.”

When scientists began the foster program, only about 50 whoopers remained in the wild, all members of a single flock that migrates 2,500 miles from Wood Buffalo National Park in Canada to Aransas National Wildlife Refuge on the Gulf Coast of Texas. Another dozen of the 5-foot tall birds, which have a 7-foot span of black-tipped wings, lived in captivity at the Patuxent Wildlife Research Center in Laurel, Md.

The whooping crane population numbered in the thousands at the turn of the century, but had shrunk to 14 by 1939. Many of the flocks were decimated by the destruction of nesting grounds, and an entire flock of non-migrating whoopers was wiped out by a hurricane in Louisiana.

Fear of losing the one remaining wild flock of the crane unique to North America to a man-made accident along the heavily industrialized Gulf Coast or to a natural disaster prompted the effort to establish the foster flock.

The worldwide population of whoopers is now about 215, with 145 birds in the thriving Canadian flock and 54 in the Patuxent flock, now split between Maryland and the International Crane Foundation in Baraboo, Wis.

Despite the problems with the foster flock, Drewien sees some encouraging signs.

“It appears the bad, long drought is waning,” he said. “This is the first year it appears avian tuberculosis has subsided. Maybe things will pick up a little bit.”

Drewien is particularly encouraged by the behavior of a female reared in captivity that was placed with the foster-reared males this summer.

The female mated with one male but then he went to the center of the marsh to molt. She then paired with a second male, too late for breeding but with enough time to establish a bond.

“She’s been with this one consistently,” Drewien said earlier this fall. “Maybe she likes this one.”

Drewien said whoopers won’t mate until they find a compatible partner during what he called a “dating” period.

“There are far more divorces among humans,” he said.

But again there is a problem: The object of Drewien’s hope could be dead somewhere between New Mexico and Idaho.

Administrators delayed a decision on whether to recapture the female until the sandhills and whoopers had grouped in early fall at Grays Lake in preparation for the winter migration.

“A wild, flying bird is not an easy thing to catch even under the best conditions,” Drewien said. Reaching the female through a crowd of cranes “is next to impossible. They start flushing (starting up from cover).”

The female left after all the other cranes had gone. Although it was able to fly short distances and a captive female placed with the foster flock in 1977 survived the migration, another six 1977 transplants died along the route and this year’s female hasn’t been seen since it left Idaho.

“We just can’t find her,” said Lewis. Researchers in the San Luis Valley so far have not located the bird “but it’s an awful big valley,” he said.

He said it might have flown down the east side of the Rocky Mountains and could turn up in the Texas Panhandle.

Drewien and Lewis said the loss is serious because females of breeding age are very rare, especially since contaminated food killed off much of the captive flock between 1984 and 1987. The chances that the foster program will get another are slight, they said.

“It’s not like we have a stock of these things sitting around. If we lose this female this winter, then we’re back where we started,” Drewien said. But, he added, “If we can keep her alive and get her back to Grays Lake, then we’ll have some nesting.

“It (the probable loss of the female) is a disappointment but it won’t kill the project. It’s just another disappointment in a series of disappointments,” he said.