GLEN ARBOR, Mich. (AP) — Hidden 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 tree flew overhead, emitting quick, high-pitched distress calls.
The little hawk dove toward the enemy, and into a net that Smithsonian interns Tim Baerwald and Zachary Bordner had strung between steel posts. They gently untangled the brown-speckled merlin, then attached a leg band and a backpack transmission unit so the researchers could track the mother bird’s movements.
“As long as it’s properly adjusted, it will have a long and happy life,” Baerwald said before Bordner released the merlin, which returned to its nesting tree.
The mission will improve knowledge of a species that is still recovering from a significant decline caused by pesticides, including DDT, banned in 1972 after harming many birds of prey. You’re also helping the managers of Sleeping Bear Dunes National Lakeshore protect the Piping Plover, an endangered shorebird. which the merlins kill and eat.
“The merlins are a huge threat to their recovery,” said Nathan Cooper, a research ecologist at the Smithsonian’s National Zoo and Conservation Biology Institute.
The situation is ironic: one species in distress bounces back thanks to restoration efforts, only to make matters worse for others in distress by preying on them or outcompeting them for food and living space. Similar circumstances have surfaced elsewhere, challenging wildlife experts who want everyone to thrive in healthy, balanced environments.
For example, the return of the iconic bald eagle has put pressure on rare waterfowl. The resurgence of peregrine falcons threatens California least terns and western snowy plover roosting on naval bases near San Diego. And, off the California coast, attacks by protected white sharks are making it difficult for threatened sea otters to recover.
Gray seals that were once on the verge of extirpation in New England waters now occupy hundreds of Massachusetts beaches. The return of the 800-pound mammal has raised concerns about vulnerable fish populations.
Such unintended consequences don’t necessarily reveal flaws in the US 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 times when we have these interspecies conflicts that we’re trying to protect,” said Stuart Pimm, an extinction specialist at Duke University. “But is it a major conservation concern? Nope.”
Species recovery can produce 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 that these things happen in are a little bit out of whack because we’ve altered 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 ones that are already in decline.”
The Great Lakes region has an estimated 65 to 70 pairs of Ring-necked, Sandy-backed Piping Plovers, which glide along the beaches nibbling on small marine animals and eggs. They are among the three remaining populations in North America, their decline caused primarily by habitat loss and predation.
Meanwhile, the number of merlins in the region has increased. In the last 10 to 15 years, at least 57 adult plovers are suspected to have been killed, Cooper said.
While officials have shot at some merlins, they are seeking non-lethal controls. The data from the transmitting backpacks could help determine whether it’s worth trying to capture and relocate them, said Vince Cavalieri, a national lakeshore biologist.
EAGLES THREATEN RARE BIRDS
The recovery of America’s national bird, the bald eagle, is a triumph. But in one area of coastal Maine, the great raptor poses a problem for the only breeding population of great cormorants in the US.
“When disturbed by eagles, adult cormorants run out and leave their nests,” said Don Lyons, a conservation scientist with the National Audubon Society’s Seabird 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 team organizes volunteers to camp near cormorant gatherings to ward off eagles.
In southern California, least terns and snowy plovers are no match for peregrine falcons, which, like eagles, rebounded after the DDT ban. These pesticides travel up food chains and cause large birds to produce eggs with thin shells, which females crush when trying to hatch them.
The San Diego Zoo and Wildlife Alliance tries to protect endangered birds by hiring a falconer to capture troublesome peregrines, keeping them in a holding facility over the winter, or releasing them in Northern California. Some find new territory, while others return, said Nacho Vilchis, a conservation ecologist.
“If there’s a bird with real problems that keeps coming back, we can ask permission for lethal removal, but that’s rarely done,” Vilchis said.
Hunting and bounties devastated New England gray seals. Saved by the Marine Mammal Protection Act of 1972, the population has rebounded into the tens of thousands.
Fishermen’s groups say seals could threaten cod stocks that regulators are struggling to rebuild after decades of overfishing.
The Coastal Ecosystem Alliance, based in Fairhaven, Massachusetts, wants to weaken the protection law to allow hunting and slow the growth of the seal population, said Peter Krogh, a member of the board.
“Grey seals are certainly this case where recovery has been cause for celebration and cause for concern,” said Kristina Cammen, a marine mammal scientist at the University of Maine, who says they are less dangerous to fish populations than the humans.
seals, cormorants harass fishermen
Like the fight over seals and cod, there are other cases where reviving species can be more of a nuisance to people than a threat to other wildlife.
Southern fish farmers and fishermen in the Great Lakes region and the Pacific Northwest have long complained about the double-crested cormorant, a dark-feathered diving bird that gorges on catfish, perch, salmon and other prized species .
Cormorants have done so well since the DDT ban that agencies have tried to limit them in some places with egg oil, nest destruction and even shooting, prompting lawsuits from environmentalists who say the birds are a scapegoat. of human actions that harm fish.
“They’re part of our avian community and our ecosystems, and you need 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 were widespread in North America before European colonization, but were reduced to tens of thousands by the 1930s and disappeared from many states. They are now hunted in all 49 states and are so common in New England that they often cause traffic jams.
Some hunters say hungry turkeys are outcompeting grouse, which are declining in parts of their range, like the upper Midwest. But scientists point to habitat loss and climate change.
The National Wild Turkey Federation is helping move turkeys from states with abundance, such as North Carolina, Maine and West Virginia, to Texas and others that may need more, said Mark Hatfield, national director of conservation services.
“If you introduce the hunting of wild turkeys locatedit reduces the problem of turkey oversupply right away,” Hatfield said.
NATURE AT WORK
Conflicts between recovering species and those still in trouble don’t always mean something is wrong, scientists say. It could reflect a return to how things were before humans got in the way.
“When a population returns to having the same interactions with other organisms as it did before it disappeared, it’s nature at work,” said John Fitzpatrick, director emeritus of Cornell University’s Laboratory of Ornithology.
The bald eagle is “challenging our preconceived notions about what’s normal” for prey like great cormorants in New England and common guillemots on the West Coast, which may have been less abundant before eagles declined, the Audubon Society’s Lyons said. .
The eagle’s recovery “complicates the conservation of other species,” Lyons said. “But his recovery is a wonderful result…it’s a welcome complication.”
Predator-prey relationships are complex and intervening can be tricky, the wildlife federation’s Stein said. It’s often wiser, she said, to focus on protecting habitat and reconnecting fragmented landscapes to promote natural migration than “moving things around.”
But environmental scientist Ian Warkentin, a specialist in merlins, said there may be ways to help struggling species without being overbearing. Larger falcons, such as peregrine falcons that are sometimes used to chase birds at airports, could be deployed to scare merlins away from plovers nesting areas.
“I’m on the side of the fence that says we should do everything we can … to help the recovery of the species we’ve caused so much pain for,” said Warkentin, of Memorial University of Newfoundland’s Grenfell campus.
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Larson reported from Washington, DC and Whittle from Portland, Maine.
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On Twitter follow Flesher: @JohnFlesher; Larson @LarsonChristina and Whittle: @pxwhittle