As species recover, some threaten others in worse shape

GLEN ARBOR, Mich. (AP) – In a forest near Lake Michigan, two scientists attached a backpack tracking device to a merlin they had caught in a net. The mission: help prevent predatory species from devouring the piping plovers – critically endangered shorebirds that nest nearby.

Merlins themselves went downhill decades ago, but are recovering, thanks to bans on pesticides like DDT. That’s good for them — but not for the flowers in the Great Lakes region, where there are only 65 to 70 pairs left. Young hawks “are a big threat to their recovery,” said Nathan Cooper, a research ecologist with the Smithsonian’s National Zoo and Conservation Biology Institute.

The situation is ironic. A problem species recovers thanks to recovery efforts, only to make things worse for others at risk by preying on them or competing with them for food and living space. Similar conditions have emerged elsewhere, challenging wildlife experts who want everyone to thrive in balanced, healthy environments.

For example, the return of the iconic bald eagle has put pressure on rare waterfowl. The resurgent threat to California’s hawks has endangered the California lesser terns and western snowy hawks that take refuge at naval bases near San Diego. And, off the coast of California, attacks by protected white sharks are preventing the recovery of endangered sea otters.

Gray seals that were once on the brink of extinction in New England waters are now taking over some Massachusetts beaches by the hundreds. The return of the 800-pound mammal has raised concerns 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 the complexity of nature and the importance of protecting biological communities, not just individual species.

“Clearly there are cases where we have these conflicts between species that we’re trying to protect,” said Stuart Pimm, an extinction expert at Duke University. “But is it a major conservation concern? No.”

Species recovery can involve trade-offs, as some animals are more adaptable than others to changes in climate or landscape, said Bruce Stein, chief scientist for the National Wildlife Federation.

“A lot of ecosystems where these things happen are a little bit off at first because we’ve changed them in some way,” Stein said. “With climate change, there will be winners and losers. The losers will tend to have specific habitat requirements, narrow ecological niches and will often be the ones already declining.”


Smithsonian interns Tim Baerwald and Zachary Bordner trapped the merlin at Sleeping Bear Dunes National Lakeshore with the help of its natural enemy: a great horned owl. This one was dead, but it was equipped with remote control devices to make it rise and flap its wings.

The Merlin raced overhead, high-pitched, rapid-fire distress calls. He sank into a net stretched between steel poles. The scientists gently untangled the brown-spotted female, then attached the tracker and a leg band.

“As long as it’s properly placed, it’s going to have a long and happy life,” Baerwald said before Bordner released the merlin, which clipped back into its nesting tree.

Merlin numbers in the area have skyrocketed since DDT was banned in 1972. They are suspected of killing at least 57 adult piping plovers in the past 10 to 15 years, said Cooper of the Smithsonian.

Ring-necked sandbacks skim along beaches snacking on tiny marine animals and eggs. They are among the three remaining populations in North America, with their decline mainly due to habitat loss and predation.

While officials have shot some merlins, they are looking for non-lethal controls. Data from transmitter backpacks could help determine whether it’s worth trying to capture and relocate them, said Vince Cavalieri, a biologist at the National Lakeshore.


The recovery of America’s national bird, the bald eagle, is a triumph. But in one area of ​​coastal Maine, the large predator is a problem for the only breeding population of great cormorants in the US.

“When disturbed by eagles, adult cormorants will flush and abandon their nests,” said Don Lyons, a conservation scientist at the National Audubon Society’s Seabirds Institute.

Then gulls, ravens and ravens swoop in to devour cormorant eggs and chicks. “If this happens repeatedly, an entire colony can fail,” Lyons said.

His group organizes volunteers to camp near cormorant gatherings to scare away the eagles.

In Southern California, lesser terns and snowy hawks are no match for peregrine falcons, which soared like eagles after DDT was banned. Such pesticides pass through food chains and cause large birds to produce thin-shelled eggs, which the females crush when they try to incubate them.

The San Diego Zoo and Wildlife Alliance is trying to protect endangered birds by hiring a falconer to capture problem peregrines, keeping them in a holding facility over the winter or releasing them in Northern California. Some find a new area, while others return, said Nacho Vilchis, a conservation ecologist.

“If there’s a real problem bird that keeps coming back, we might ask for a permit for lethal removal, but that’s only rarely done,” Vilchis said.

Hunting and bounties decimated New England gray seals. Saved by the Marine Mammal Protection Act of 1972, the population has recovered to the tens of thousands.

Fishing groups argue the seals could threaten cod stocks that regulators are struggling to rebuild after decades of overfishing.

The Coastal Ecosystem Alliance, based in Fairhaven, Mass., wants to weaken the protection law to allow hunting and slow the growth of the seal population, board member Peter Krogh said.

“Grey seals are definitely that case where the recovery has been cause for celebration and concern,” said Kristina Cammen, a marine mammal scientist at the University of Maine who says they pose less of a threat to fish populations than humans.


Like the conflict over seals and cod, there are other cases where species resurgence may be more of a nuisance to humans than a threat to other wildlife.

Fish farmers in the South and fishermen in the Great Lakes and Pacific Northwest have long complained about the double-crested cormorant, a dark-winged diving bird that preys on catfish, perch, salmon and other prized species.

Cormorants have done so well since the DDT ban that agencies have tried to contain them in some locations with egg oil, nest destruction and even shooting — drawing lawsuits from environmentalists who say the birds are scapegoating human actions that harm them. fish.

“They are part of our bird community and our ecosystems, and there needs to be a place for them,” said Dave Fielder, a research fisheries biologist with the Michigan Department of Natural Resources. “But when their numbers are so high that they potentially decimate recreational fisheries, that’s a problem.”

Wild turkeys had spread across North America before European settlement, but had dwindled to tens of thousands by the 1930s, extirpated from many states. They are now hunted in 49 states and are so prevalent in New England that they often cause traffic jams.

Some hunters say hungry turkeys compete with grouse, which are declining in parts of their range, such as the Upper Midwest. But scientists point to habitat loss and climate change.

The National Wild Turkey Federation helps move turkeys from abundant states — such as North Carolina, Maine and West Virginia — to Texas and others that could use more, said Mark Hatfield, national director of conservation services.

“If you introduce hunting of local wild turkeys, you will immediately reduce the problem of overabundant turkeys,” Hatfield said.


Clashes between recovering species and those still in trouble don’t always mean something is wrong, scientists say. It could reflect a return to the way things were before humans took to the streets.

“When a population returns to where it has the same interactions with other organisms as it did before its decline, that’s nature at work,” said John Fitzpatrick, director emeritus of Cornell University’s Laboratory of Ornithology.

The bald eagle “challenges our preconceived notions of what’s normal” for prey such as great cormorants in New England and common loons on the West Coast, which may have been less abundant before the eagles’ decline, Lyons said. Audubon Society.

Eagle recovery “complicates the conservation of some other species,” Lyons said. “But their recovery is such a wonderful result … this is a welcome complication.”

Predator-prey relationships are complex and intervention can be difficult, said the wildlife federation’s Stein. It’s often wiser, he said, to focus on protecting habitats and reconnecting fragmented landscapes to promote natural migration rather than “moving things willy-nilly.”

But environmental scientist Ian Warkentin, a Merlin expert, said there could be ways to help struggling species without being heavy-handed. Larger hawks – such as the peregrines that are sometimes used to chase birds from airports – may be deployed to flush merlins from flower nesting areas.

“I fall on the side of the fence that says we should do everything we can … to help restore the species we’ve caused such grief for,” said Warkentin, of Memorial University of Newfoundland’s Grenfell Campus.


Larson reported from Washington, DC and Whittle from Portland, Maine.


On Twitter follow Flesher: @JohnFlesher; Larson @LarsonChristina and Whittle: @pxwhittle

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