MassWildlife on mission to save roseate tern from extinction

PENIKESE ISLAND, BUZZARDS BAY — A watercolor splash of pink draws the eye on Penikese Island as Marcela Liljesthröm — under a pink umbrella and draped neck to knee in a plastic pink poncho — moves through the gray fog canvas like a living beach rose. The outfit protects her from frenzied gull attacks as she examines bird nests, eggs, and chicks.

Liljesthröm is a seasonal seabird biologist for the Massachusetts Division of Fisheries and Wildlife, which oversees the Penikese Island Wildlife Sanctuary. As one of its many conservation missions, MassWildlife has been working for the last three decades to bring the roseate tern back from the brink of extinction.

In a conservation success story, these efforts are working, offering hope for the roseate tern’s recovery, Carolyn Mostello, coastal waterbird biologist with MassWildlife, said in a telephone interview. 

“It’s very exciting and gratifying when things go in the right direction,” Mostello said.

Holding tight to the umbrella as she walks on Penikese, Liljesthröm carefully checks on gull chicks on the 75-acre island. The birds are sensitive to human disturbance and put on an aggressive defense, diving in close, taking aim, and dropping bombs of liquid poop. Liljesthröm’s umbrella and poncho are covered in white streaks and splotches. The common and roseate terns she will visit later on the other side of the island are just as aggressive, though much smaller. 

Named for the rosy blush on its chest, the roseate tern was listed as a federal and state endangered species in 1987. More than 60 percent of all North American roseates breed in Buzzards Bay, making the region key to conservation. The bird’s numbers plummeted due to habitat loss and predator pressure, including humans hunting the birds for their feathers and speckled eggs in the late 1800s and early 1900s, and the birds have struggled to make a comeback. 

On Penikese, Liljesthröm’s cautious movements in the nesting colony reflect the careful dedication needed to protect this vulnerable bird whose survival depends on annual human intervention. The deliberate and steady efforts by bird scientists in Massachusetts to restore nesting habitat and reduce disturbance and predation have made a difference.

A key element of roseate tern recovery is restoring populations of common terns, a state-listed bird of special concern. In the Northwest Atlantic, the roseate tern will not nest without its more aggressive cousin, which provides protection from predators and intruders for the colonies.

Last year, the Bay State hosted more than 4,000 nesting pairs of roseate terns, tripling the population from a decade ago. This is significant progress, especially as three small Massachusetts islands in Buzzards Bay — Penikese Island, Bird Island, and Ram Island — host more than 60 percent of the Northwest Atlantic’s roseate terns during breeding season from May through July. After the summer, most head to the north and east coasts of South America for fall and winter.

Town-owned Bird Island off Marion and state-owned Ram Island Wildlife Sanctuary off Mattapoisett provide nesting grounds for the majority of the roseate terns in the bay. 

Penikese, which sits about an hour’s boat ride from New Bedford or Woods Hole in the Elizabeth Islands, has a tiny population of roseate terns in comparison, but like the others, it has witnessed encouraging signs of recovery. The number of nests has doubled over the last few years to more than 40 this year, although the island’s numbers can fluctuate quite a bit from year to year. Importantly, common tern numbers are healthy on Penikese, reaching a record high of 1,800 pairs this year.

Mostello said having a few different sites where terns can turn is critical, especially when there are disasters in one of the colonies, such as the Bouchard B-120 oil spill in 2003 that damaged nesting grounds on Ram Island. If the terns have no alternative, breeding will be disrupted in an already fragile population.

Fashion it turns out was almost the death of the roseate terns. Hunters seeking colorful plumes for women’s hats and speckled eggs for oologists, who study or collect bird eggs, killed the adult birds in large numbers and reduced the next generations of roseate terns when they raided the nests. Although hunters and collectors no longer threaten the roseate terns, the birds remain vulnerable today.

They are under threat from a host of predators as well as human developments and climate change, which can reduce habitat and shift the prey that terns rely on for their diets. Nesting islands are scarce, as many were taken over by nesting gulls during the 20th century and the terns were never able to regain footholds. Today 90% of the roseate terns in the U.S. nest on just three islands: Bird and Ram in Buzzards Bay and Great Gull Island in New York.

During the day, while under siege from protective bird parents who screech, swoop, and poop, Liljesthröm studies nest success and chick survival, counts nests for annual censuses of terns and other bird species to track population trends, and bands terns to contribute to studies of survival and movements.

At night, she plays the Back Street Boys. She isn’t a fan. She’s hoping that black-crowned night herons aren’t either. The herons fly stealth in the dark over the roseate tern breeding area, locating nests to maraud by listening for the telltale cheeping sound of chicks working to break out of their shells. To help mask the chicks’ noises and scare the night herons, the biologists have rigged up speakers to play music and podcasts through the night. The method has met with mixed success on Penikese but has been helpful elsewhere in Buzzards Bay, Mostello said.

Gull predation is a daytime danger. Both the gulls and the herons can be quick and efficient in their attacks on tern eggs and chicks. When a predator is spotted, the terns set off warning cries and rise in a swarm to chase the raider. 

Providing welcoming grounds for the terns to nest is an important part of the conservation efforts. Creating these conditions has involved a multi-pronged approach, Mostello said. 

On Penikese, controlled burns and herbicide treatments have been used to discourage invasive shrubs and vines and maintain open areas where common terns, especially, prefer to nest. Hand-weeding is also sometimes necessary to ensure that tern parents have places to land and feed their chicks the fish they’ve caught. 

Nest boxes have been installed in some areas to provide extra opportunities for roseate terns, which prefer to set up house under vegetation or other cover.

Whole-island restorations are critical for maintaining healthy tern populations in Buzzards Bay, Mostello said. She points to low-lying Bird Island, which a decade ago underwent stabilization and nourishment restoration (sand placement) to restore nesting grounds for terns. This appears to be a major factor in roseate terns’ comeback in Massachusetts. Ram Island is awaiting similar efforts.

As part of the Penikese Island Wildlife Sanctuary, MassWildlife also protects and studies other nesting waterbirds, including great black-backed gulls, American herring gulls, double-crested cormorants, and American oystercatchers.

The public can visit but must respect strict rules to not disturb the birds, such as not bringing dogs on the island and sticking to mowed trails. Getting to Penikese requires a private boat or planned tour, such as those offered occasionally by Mass Audubon or The Penikese Island School, which also organizes nature camps for middle schoolers and school field trips to the island.

Natalie A. White is a freelance journalist and editor and former reporter covering the SouthCoast. She grew up and lives in Southeastern Massachusetts.