Published online 11 February 2011 | Nature | doi:10.1038/news.2011.88

News

Whooping cranes head back to Louisiana

Conservationists hope fourth attempt to reintroduce endangered bird to the wild will be a success.

craneEndangered whooping cranes were once common in Louisiana.Photo Researchers/FLPA

Officials with the Louisiana Department of Wildlife and Fisheries (LDWF) are finalizing plans to release a small flock of whooping cranes (Grus americana) in a protected wetland, in what could be a promising step towards long-term viability for an endangered species. The move would represent the return of a long-lost native — absent from the state for more than 60 years.

Officials say that ten captive-bred birds will be flown by plane from their Maryland hatching ground to the White Lake Wetlands Conservation Area in Vermilion Parish, southwestern Louisiana, as early as next week. Once released into the wild, they will be monitored by the LDWF. The department hopes to establish a non-migratory flock of whooping cranes in White Lake over the next ten years to help ensure the survival of the species.

The effort is the latest in a series of attempts to increase the numbers and range of the striking 1.5-metre tall white-and-black birds, whose population dwindled to just 21 individuals in 1941 as a result of habitat loss and hunting.

Conservationists' efforts over the past 35 years have yielded a modest recovery. The last remaining natural flock, the Aransas–Wood Buffalo population, which migrates between Canada and Texas, has bounced back to around 260 birds.

But researchers have been trying to establish further flocks. "We don't feel comfortable relying just on that one flock as a safeguard," says Tom Stehn, whooping crane coordinator for the US Fish and Wildlife Service at Aransas National Wildlife Refuge in Texas and co-leader of the International Crane Recovery Team.

Ideally, officials would like to establish two more self-sustaining populations. The US Fish and Wildlife Whooping Crane Recovery Plan stipulates that if two established populations of birds maintain 25 nesting pairs each for 10 consecutive years, and the natural population has at least 40 nesting pairs, that could be enough to upgrade the conservation status of the birds from endangered to threatened.

That goal is still at least 30 years away, says Stehn. "Each reintroduction we try does better, but we haven't reached a level where it's helping recovery."

Fourth time lucky

The Louisiana reintroduction marks the fourth attempt to establish a new whooping crane population in the wild. In 1975, scientists tried unsuccessfully to use sandhill cranes (Grus canadensis) in Idaho as foster parents for the birds. A stationary flock of whooping cranes established in Kissimmee, Florida, in 1993 did well for some years, but loss of numbers as a result of drought, starvation and predation led to the project being abandoned.

A third attempt, begun in 2001, formed the eastern migratory population, which now numbers around 100 birds. Cranes raised in captivity in Maryland are taught to migrate between Wisconsin and Florida by following ultralight aircraft. This flock has had more success than the previous two, but the birds have been slow to start reproducing on their own. They're laying eggs but few hatch, possibly because parasitic black flies (Simulium annulus and Simulium johannseni) are driving the parents from their nests before hatching. This has raised concerns about the flock's ability to sustain itself. A project this year may help determine whether the flies are the real problem.

So experts hope that the fourth time will be the charm in Louisiana, where the LDWF has helped to bring back both the American alligator (Alligator mississippiensis) and the brown pelican (Pelecanus occidentalis). Stehn says that White Lake is the first reintroduction site with historially documented nesting data, so it could be just the right habitat for the birds. "We're finally doing what we probably should have done in the very beginning," he says.

"Coastal Louisiana is a giant wetland with a mosaic of different wetland types," says Bill Brooks, a biologist at the US Fish and Wildlife Service in Jacksonville, Florida. Southwestern coastal Louisiana has 1.3 million acres of marsh, open water and Chenier habitat that support a rich variety of bird species, he adds, giving the flock "a higher chance of being successful".

To be extra sure the White Lake area is a suitable habitat for the cranes, LDWF officials monitored the area around their pen enclosure for a year to ensure that food will be available to the cranes year-round, and it isn't a hangout for predators or a hatching ground for black flies.

"We've taken every precaution that we think is necessary to give them the best leg up," says Carrie Salyers, a biologist at the LDWF's Rockefeller Wildlife Research Center in eastern Cameron Parish. Officials also worked closely with stakeholders in the area, including residents and business owners, to get them onboard with the reintroduction effort.

Later this month, the ten cranes will arrive from the US Geological Survey Patuxent Wildlife Research Center in Laurel, Maryland, where they were raised. They will be housed first in an enclosed protective pen, then in one that is open to the wild. Officials will monitor them daily and track them by satellite. If all goes well, more birds will be introduced each year for at least the next ten years. But only time will tell whether the flock will sustain itself and contribute to the North American whooping crane population.

"Wild-born animals that are raising their own chicks are going to be the true measure of recovery," says Brooks. 

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