Just as it can with human couples, sharing a good meal apparently sparks thoughts of love among whooping cranes.
The stately, endangered birds at Patuxent Wildlife Research Center in Laurel are being primed by their keepers for another season of carefully orchestrated mating with a "special breeder diet."
No chocolate or oysters, though, just subtly enriched pellets of the cranes' usual prepared bird food.
"We give them a little more calcium, a little more protein," said Jonathan Male, who supervises the center's whooping crane propagation effort.
It's just one of the many human assists that North America's tallest birds get as they continue a long struggle to recover from the brink of extinction. They've been shot at, preyed on by bobcats, driven off their nests by biting flies and even grounded for a time this winter by the Federal Aviation Administration.
But under the constant ministrations of wildlife specialists and volunteers in the United States and Canada, the number of whooping cranes has gradually recovered from just 16 in the 1940s to 437 now in four flocks, three built from scratch. Another 162 are being kept in captivity, where they're coaxed to augment the frustratingly meager reproduction of the reintroduced flocks.
The 235-acre Laurel center run by theU.S. Geological Surveyis a linchpin in the international effort, with a program there since 1967 to breed the long-legged birds with the snowy white feathers, red cap, long black bill and distinctive bugling call.
Last year, Patuxent produced about 20 chicks from its flock of 72 penned whooping cranes. About half were flown to Wisconsin to join a reintroduced "eastern" flock of more than 100 cranes that migrates to Florida every fall. The others were released into small nonmigratory flocks in Florida and Louisiana.
The last "natural" flock — the 16 surviving birds from which all the others are descended — has rebounded on its own to 278 birds. It splits time between the Aransas National Wildlife Refuge on the Texas coast in winter and its summer nesting grounds in Canada's Northwest Territory. But it faces a series of challenges, including drought, rising sea level and encroaching development. Wildlife experts are trying to establish new flocks of captive-reared birds in other places in case disaster befalls the Texas-Canada group.
The eastern flock made news recently after a group of young chicks hatched at Patuxent was grounded on its maiden migration flight from Wisconsin to Florida. Federal aviation regulators had questioned whether the human volunteers leading the young birds in ultralight aircraft were properly licensed. After the birds spent nearly a month penned up in Alabama, their guides with the conservation group Operation Migration were finally freed to resume the journey. The flock has yet to really get going, though, thwarted by high winds and a few chicks' apparent reluctance to depart their interim home.
The run-in with the FAA was just the latest hurdle for the eastern flock, which has been the focus of rebuilding efforts for several years. Wildlife specialists feel good about the progress in establishing the flock but are concerned about its long-term viability.
"They're migrating well, their survival is pretty darn good, and they're finding good habitat in winter and summer," said John B. French Jr., research manager at Patuxent.
But the reintroduced birds haven't produced young. Only three chicks hatched in the wild in Wisconsin have grown big enough to fly, according to a report by the U.S. Fish and Wildlife Service, which oversees recovery efforts.
As a result, experts are tinkering with the birds' nesting habitat in western Wisconsin and considering changes in the captive breeding program at Patuxent to see whether the cranes can be helped to be more attentive parents.
Biologists suspect that mating pairs in Wisconsin might be driven to abandon their nests by springtime swarms of biting flies. Officials tried suppressing the black fly hatch last year by spraying with a bacterial pesticide and saw a slight uptick in crane reproduction. Four chicks hatched out of 22 nesting attempts, but none survived.
Scientists are weighing whether they can avoid the fly problem by getting cranes to lay eggs later. Taking the cranes' eggs shortly after they're laid in most cases prompts them to lay a second clutch two or three weeks later. That delay might be enough to get nesting past the worst of the flies, French said. The purloined eggs could be taken to Patuxent and other captive breeding sites for hatching.
Another option might be to shift the reintroduced cranes' nesting ground in Necedah National Wildlife Refuge to a less fly-infested spot. Meanwhile, French said, some have suggested tinkering with the captive breeding program, which relies on nonendangered sandhill cranes to incubate many of the whooping crane eggs and then on human staff, dressed in crane costumes, to work with them after hatching.