CHATHAM - Each year, it seems that there are more protected piping plovers nesting on area beaches than the year before. Ospreys, once on the brink of extinction, can be seen everywhere. And don't even start with seals, which can be found by the tens of thousands on Monomoy but are protected by federal law. If you’ve ever wondered why, you’re not alone.

Piping plovers

Given the number of times they show up in news headlines, the agitation they engender when they cause beach closures, and fairly regular reports that they’re nesting locally in increasing numbers, one might think that piping plovers are more numerous than they are. But the diminutive, hard-to-spot shorebirds remain very rare, at least on a global scale.

Plovers are classified as “threatened “ under the federal Endangered Species Act, and have a corresponding designation under state law. In 1986, there were 140 breeding pairs in Massachusetts, a number that’s now close to 700. For many years, there were more nesting pairs of piping plovers in Chatham than there were in most of the states on the East Coast.

Matthew Hillman, the manager of the Monomoy National Wildlife Refuge, said while the Cape still has among the highest nesting densities on the East Coast, “that’s still not the case on the international scale.” Piping plovers breed here, but spend most of their lives along the Gulf Coast and in the Caribbean. While East Coast piping plovers are classified as threatened, a sub-population living on the Great Lakes has far fewer numbers and is listed as endangered.

Plovers face all kinds of perils, aside from the dangers that chicks encounter when nesting on our beaches. They are a favorite food for all kinds of predators, including snowy owls. They are susceptible to habitat destruction from storms, as well.

“They had a really difficult winter in the Bahamas and the Caribbean,” Hillman said. “They got hit by hurricane after hurricane.”

Because their numbers are growing, it is theoretically possible for plovers to eventually recover to the point where they reach their “biological carrying capacity,” the population size that is the maximum that can be sustained by the environment. So when will plovers reach the point at which they can be removed from the threatened species list?

“Never,” said ornithologist Mark Faherty of Mass Audubon’s Wellfleet Bay Wildlife Sanctuary. “This isn’t the bald eagle, right?” he said. Bald eagles were saved from the brink of extinction, and are are now well established in a wide area, and were removed from the endangered and threatened species lists in 2007. But plovers require some level of maintenance protection, including steps to keep people from inadvertently disturbing their nesting sites, he said.

“If we walk away from plover protection, how many years until they’re endangered?” Faherty said. Conflicts between people and plovers are limited to certain areas and certain times, and are being addressed with habitat conservation plans like the ones in place in Orleans and Chatham. When it comes to those conflicts, “we’re working on that problem in new ways,” he said.

Still, Hillman said the ultimate goal for plovers and other threatened species is to get them “de-listed” from the Endangered Species Act protections. And the bald eagle isn’t the only species that’s had that kind of success.

Ospreys

While plovers were hunted for their feathers and later lost habitat to coastal development, the prime threat to raptors like bald eagles and ospreys was DDT. The pesticide was used widely after World War II, and it polluted the birds’ food supplies. Ospreys nearly vanished because the chemical caused their egg shells to be abnormally thin, and by 1965, there were just 11 nesting pairs in Massachusetts. When DDT was outlawed in 1972 and nesting platforms were erected, the population rebounded.

Now, osprey are much more abundant, with hundreds of nesting pairs on the Cape.

“You have this amazing success story,” Hillman said. Osprey are no longer protected as an endangered species, but they’re still facing population pressures. Wintering in South America, osprey frequently nest near fish farms, where they’re shot and killed by farmers, he said.

“These are pressures that we, as New Englanders, don’t necessarily think about,” he said. In fact, one of the great challenges when it comes to protecting migratory birds is the realization that different countries have different laws, and many don’t highly value bird conservation. That’s not a new problem. Ospreys and most other local birds are still protected under the Migratory Bird Treaty Act of 1918.

It’s widely known that nesting ospreys usually can’t be disturbed even when their nests are in inconvenient locations – like docks, construction equipment, the lights over the athletic field at Monomoy High School or the radio tower at the police station. Under the Act, osprey nests can be removed without a permit if the nest shows no signs of eggs or young present, though anyone removing a nest would be wise to carefully document that fact.

One consequence of their population recovery is the proclivity of osprey to nest on utility poles, a practice that regularly causes power outages and small fires. A team at Eversource has a special permit allowing such nests to be removed when necessary, and the utility often erects “deterrent devices” on poles favored by osprey. They also erect nesting platforms to encourage nests in safer locations.

Gray seals

There’s simply no arguing the abundance of gray seals off Chatham. Their population numbers appear to be increasing, and they are frequently faulted by commercial fishermen for eating their catch before it can be harvested or depleting certain stocks. They are almost certainly the cause of the increase in great white shark numbers off area beaches as well. And while they’re not an endangered species, they are very heavily protected by law.

In this case, the legislation is the Marine Mammal Protection Act, which offers all marine mammals strong protections against hunting and harassment. Passed in 1972, the legislation has been a critical tool in the protection of whales, sea otters, dolphins, walruses, and even polar bears. Fisheries biologist Kimberly Murray, who coordinates seal research at the Northeast Fisheries Science Center, said there can be as many as 25,000 gray seals on Monomoy Island during their molting season, and they breed in great numbers during the winters on Muskeget Island, Monomoy and Noman’s Land off Martha’s Vineyard.

An experienced commercial fisherman recently told the Chronicle that he observed a wide band of seals – five or six deep – along many miles of Monomoy’s shoreline. So how many seals do there need to be before conservation efforts are unnecessary? That question can be defined for animals covered by the Endangered Species Act, but the answer’s more elusive for marine mammals.

“The Act doesn’t specify a point at which a species has fully recovered and can be de-listed,” Murray said. The goal of the legislation is to maintain populations an an optimal sustainable level, but “it’s kind of a gray area exactly what that number is,” she said. If a seal population were at its natural maximum, there would be signs like massive die-offs or a slowing in reproduction. “We don’t see that yet,” Murray said.

Some have advocated thinning the number of seals off Monomoy, but that’s hard to imagine, Faherty said. Though he understands those who argue that the population is healthy and doesn’t need further protection, it’s not clear how such a culling would happen – even if the law allowed it.

“What, would you machine-gun the colony?” he asked. Gray seals are not like white-tailed deer and other species that are legally hunted, he said. “The way society is now, I just don’t think culling would pass muster,” Faherty said.

But because the act has no means for de-listing species, it could quite possibly take an act of Congress to reverse protections for gray seals. In any case, there’s no biological evidence yet supporting that idea.

“Maybe there is a point in the future where our management practices change in the case of gray seals, but we’re not there yet,” Hillman added. “There were no seals on Cape Cod in the 1970s,” he said, and as a nation, Americans supported the Marine Mammal Protection Act and the Endangered Species Act because they believed that those animals needed to be protected from extinction.

“There’s a very good reason for that,” he said. “I think it’s important for us to stay on that course.”

Like osprey and piping plovers, gray seals range beyond the United States. They travel widely and rely on Chatham’s unique geography for key parts of their life cycle.

“These aren’t just regional issues, they aren’t Cape Cod issues,” Hillman said. “These are international issues.”

Officials say it’s sometimes hard to notice the global rarity of animals when they’re ubiquitous here at home. Chatham is home to large plover populations, a record-setting tern colony, a white shark “hot spot,” and world-class sportfishing. So it’s not hard to lose track of “the embarrassment of riches that Chatham has,” Faherty said.

Email Alan Pollock at alan @capecodchronicle.com
Twitter: @CCCAlanPollock