Concealed behind trees near Lake Michigan, two scientists remotely manipulated a robotic owl on the forest floor. As the intruder flapped its wings and hooted, a merlin guarding its nest in a nearby pine darted overhead, sounding high-pitched, rapid-fire distress calls.

The small falcon dove toward the enemy — and into a net that Smithsonian interns Tim Baerwald and Zachary Bordner had stretched between steel poles. They gently disentangled the brownish-speckled merlin, then attached a leg band and a backpack transmission unit so researchers could trace the mother bird’s movements.

The mission will enhance knowledge of a species still recovering from a significant drop-off caused by pesticides including DDT, banned in 1972 after harming many birds of prey. It also is helping Sleeping Bear Dunes National Lakeshore managers protect the piping plover, an endangered shorebird that merlins kill and eat.

“Merlins are a big threat to their recovery,” said Nathan Cooper, a research ecologist with Smithsonian’s National Zoo and Conservation Biology Institute.

The situation is ironic: A troubled species rebounds thanks to restoration efforts, only to make things worse for others in peril by preying on them or outcompeting them for food and living space. Similar circumstances have turned up elsewhere, challenging wildlife experts who want them all to thrive in balanced, healthy environments.

For instance, the iconic bald eagle’s comeback has pressured rare water birds. Resurgent peregrine falcons menace endangered California least terns and Western snowy plovers that take refuge at naval bases near San Diego. And, off the California coast, attacks from protected white sharks hinder recovery of threatened sea otters.

Gray seals previously on the brink of extirpation in waters of New England now occupy some Massachusetts beaches by the hundreds. The 800-pound mammal’s return has raised worries about vulnerable fish stocks.

Such unintended consequences don’t necessarily reveal flaws in the U.S. Endangered Species Act or conservation programs, experts say. Rather, they illustrate nature’s complexity and the importance of protecting biological communities, not just individual species.

“Clearly there are occasions when we get these conflicts between species that we’re trying to protect,” said Stuart Pimm, a Duke University extinction specialist. “But is it a major worry in conservation? No.”

Species recoveries can produce tradeoffs, since some animals are more adaptable than others to changes in the climate or landscape, said Bruce Stein, chief scientist with the National Wildlife Federation.

“A lot of ecosystems where these things are occurring are a little out of whack to begin with because we’ve altered them in some way,” Stein said. “With climate change, there are going to be winners and losers. The losers will tend to have specific habitat requirements, narrow ecological niches, and often will be the ones already declining.”

The Great Lakes region has an estimated 65 to 70 pairs of sandy-backed, ring-necked piping plovers, which skitter along beaches nibbling tiny marine animals and eggs. They’re among three remaining North American populations, their decline caused primarily by habitat loss and predation.

Meanwhile, merlin numbers in the region have jumped. In the past 10 to 15 years, they’re suspected of killing at least 57 adult plovers, Cooper said.

While officials have shot some merlins, they’re looking for non-lethal controls. Data from the transmitter backpacks might help determine whether capturing and relocating them is worth trying, said Vince Cavalieri, a biologist with the national lakeshore.

Source: AP