NEW ORLEANS (AP) — For the first time in decades, a pair of whooping cranes in Louisiana have built a nest outside captivity. But biologists don’t expect eggs this year. The birds are too young.

The big cranes generally lay their first fertile eggs at 4 to 7 years old. Department of Wildlife and Fisheries spokesman Bo Boehringer says this female is 2 years old and the male is 3.

The department’s administrator of coastal and nongame resources says whooping cranes are very protective of their eggs. But this pair isn’t chasing away other birds, and they leave the area for days at a time.

Both officials say the experimentation is a positive step.

It’s the first known nest made by any of the 40 birds released in southwest Louisiana since early 2011.

Robert Love, the department’s administrator of coastal and nongame resources, said there’s another telling sign that this nest is a “dummy.” Whooping cranes are very protective of their eggs, but this pair isn’t chasing other birds away. Love said they also leave the area for two to three days at a time.

If one of the 27 birds in Louisiana’s experimental flock raises a chick, it would be the first recorded outside captivity in the state since 1939.

The graceful cranes stand nearly 5 feet tall with a 7 1/2-foot wingspan. Just over 500 survive, all descended from 15 that lived in coastal Texas in the 1940s.

This year’s nest, in the middle of a huge crawfish pond in southwest Louisiana, is the first biologists have seen for any of the 40 birds released at White Lake since early 2011. Love won’t say just where it is to protect the birds and the farmer’s privacy.

“Ultimately I hope we have more like a thousand whooping cranes in Louisiana, and all these farmers are making ecotourism dollars” with tours, Love said.

For now, the flock’s growth will remain slow. Once they mature, breeding pairs generally raise one chick a year. To speed things up, Louisiana’s flock and the one taught to migrate between Wisconsin and south Florida have been sharing about 25 to 45 young birds bred in captivity each year. A review this year will decide whether to continue adding young birds to Louisiana’s experimental flock. The only natural and self-sustaining flock consists of about 250 whoopers that migrate between northern Canada and Texas.

Whooping cranes mate for life, forming what biologists call a pair bond — though if one mate dies the survivor will take a new one.

“This is the only pair bond that we have,” Love said of the two that most recently built the dummy nest. “We had one last year and the male got killed by coyotes.”

He said that pair didn’t build any nests, though they jumped and tossed sticks, as cranes often do before they mate. He didn’t know whether they ever did a full-blown mating dance. Biologists haven’t seen the current pair in a mating dance, he said.

Love said Louisiana biologists called their counterparts in Florida, where whooping cranes were first led by ultralight planes in 2001, to ask what they can expect. “They said some of their young birds would make seven of these dummy nests without defending them in a single year,” Love said.

The Louisiana birds are two of 10 hatched in 2010 and released in early 2011; 12 of 16 born and released in 2011, and 13 of 14 released last December. The 14th bird released in December went missing in February, Boehringer said in an email. The bird’s transmitter stopped working, and searches turned up nothing. The bird is presumed dead, he said.

None of the birds lives around White Lake, where all 40 were released. One lives in the Rockefeller Wildlife Refuge and some are living in St. Mary Parish marshland, but most spend their time in rice fields and crawfish ponds, Love said.

“It seems like the agricultural landscape is managed wetlands that all wading birds love,” he said.

That makes farmers’ cooperation crucial to the birds’ survival.

The nesting season in central Florida runs from January to May. The eggs take about a month to hatch and fledglings can fly when they’re 80 to 90 days old, according to the Florida Fish and Wildlife Commission.

If farmers accept them and are willing to work around their nests, their fields often stay flooded into June, Love said.

“There’s not much difference between ... shallow water impoundment in Rockefeller and 6 inches of water in a rice field, from a wading bird’s standpoint — whether you’re an ibis, an egret, a black-necked stilt or a whooping crane,” he said.

And, eggless or not, the nest-building has state biologists taking notice.

“We’re excited that they’re taking a progressive step and trying to experiment,” Love said.