Venture into the waters of Buzzards Bay, Massachusetts in the spring and summer and you may well be treated to the sight of agile, graceful terns darting above and plunging into the sea. The species you are most likely to see are the Roseate Tern, Sterna dougallii, and the Common Tern, Sterna hirundo. These migratory birds arrive in Massachusetts in April and May to nest, mostly on islands, and depart again for their wintering grounds (as far south as Argentina) in August and September. Their primary foods are juvenile fish such as herring, sand lance, and mummichog. Both tern species are long-lived, with the oldest wild birds reaching their mid- to upper-20s. More detail on these species can be found on our fact sheets .

Colony Life

Common and Roseate Terns are colonial nesters. A major benefit of nesting in a colony is group defense against intruders and

Figure 1.  Common Tern chicks and egg, Penikese Island, MA.
Figure 1. Common Tern chicks and egg, Penikese Island, MA.

 predators. While Common Terns will nest in single-species colonies, Roseates will not. In this part of the world, Roseates always nest with Common Terns, which vigorously defend their nests and young against intruders -- benefiting the much more timid Roseates. This defense is necessary because eggs and young, although camouflaged with surroundings, are still vulnerable to being gobbled up by a predator or stepped on by a clumsy or inattentive human. Eggs are laid directly on the ground and chicks are "earth-bound" for about three or four weeks until they can fly (Figure 1).

A visit to a large colony of Common and Roseate Terns is not easily forgotten. Intruders are mobbed by clouds of shrieking, divebombing, defecating terns. Humans (and some other animals) may also be pecked on the head and any exposed skin mercilessly by Common Terns. You would emerge spattered and weary, but hopefully with added respect for these tenacious birds.

Because these birds are so highly vulnerable, all tern colonies in Massachusetts are off-limits during the nesting season. Colonies may only be entered for approved research or management purposes. However, they can be enjoyed (much more peacefully) from a distance through binoculars or spotting scopes. You can also watch terns on our real-time Bird Island tern web camera. The camera is active from approximately mid-May through mid-July.

History

Until the 1880s, Common and Roseate Terns were abundant in Massachusetts, with hundreds of thousands of pairs reportedly nesting at Muskeget Island (off Nantucket) alone. (See Nisbet, I.C.T. 1973. Terns in Massachusetts: recent numbers and historical changes. Bird-banding 44: 27-55.). Like many other bird species, however, terns were victims of their own loveliness. They were hunted nearly to extinction along the Atlantic Coast for their plumes, which were used to adorn hats. In Massachusetts, large numbers of terns survived at just a few locations.

The conservation movement swelled during that time period -- in great part due to outrage over the hunting of birds for their feathers. Consequently, both local and national legislation was enacted that provided legal protection for many birds. In Massachusetts, as in other places, terns responded to enhanced protection and populations partially recovered.

Starting in the 1930s, gulls (especially Great Black-backed and Herring Gulls) gained a footing in the Commonwealth and their populations exploded, aided by food from garbage dumps and discards from the fishing industry. Gulls overtook Common and Roseate Terns' preferred nesting sites -- the offshore islands that are relatively secure from predators -- and tern populations plummeted. Gull populations continued to grow through at least the 1970s. Closure of dumps and better management of fisheries waste have probably been major factors that checked the growth of gull populations; gull populations have declined substantially since their peak.

Buzzards Bay Tern Current Status

Tern populations are still struggling, although progress has been made for some species. The Roseate Tern is listed as Endangered pursuant to the U.S. and Massachusetts Endangered Species Acts. The Roseate Tern was listed principally because of the contraction of its breeding range, with many breeding sites lost (especially to gulls) and not recovered, and secondarily because of declining numbers. The Common Tern and two other species that nest in the Commonwealth -- the Least Tern, Sterna antillarum, and the Arctic Tern, Sterna paradisaea -- are state-listed as Special Concern.

In Massachusetts, most of the major nesting islands for Common and Roseate Terns are in Buzzards Bay at Bird, Ram, and Penikese Islands (Figure 2). Another key site is Monomoy National Wildlife Refuge off Cape Cod, which supports the largest Common Tern colony on the Atlantic coast. Common Terns have increased fairly steadily in the Commonwealth since the mid-1980s, although growth has slowed in recent years (Figure 3). After nearly two decades of relatively steady growth, the Roseate Tern population is in decline, both in Massachusetts and in the Northeast as a whole (Figure 4), for unknown reasons.

major tern nesting islands in MA
Figure 2. Locations and sizes (in hectares) of the major tern nesting islands in Buzzards Bay, MA.

 

Figure 3.  Number of pairs of Common Terns in Massachusetts, 1985-2009.
Figure 3. Number of pairs of Common Terns in Massachusetts, 1985-2009.

Figure 4.  Number of pairs of Roseate Terns in the Northeast U.S. and Massachusetts, 1988-2010.
Figure 4. Number of pairs of Roseate Terns in the Northeast U.S. and Massachusetts, 1988-2010.

Terns are highly vulnerable to threats such as human disturbance, habitat loss, predation, oil spills, and competition with gulls. In a given year, Common Terns usually nest at about 35 sites statewide, and Roseates at five sites. The birds, however, are highly aggregated, which greatly increases their vulnerability to threats. About 95% of Common Terns are clustered into just six sites (Figure 5). The situation for Roseates is even more serious: 95% are concentrated at just two sites (Figure 6).

Figure 5.  Number of pairs of Common Terns at nesting colonies in Massachusetts, 2009.
Figure 5. Number of pairs of Common Terns at nesting colonies in Massachusetts, 2009.

 

Figure 6.  Number of pairs of Roseate Terns at nesting colonies in Massachusetts, 2010.
Figure 6. Number of pairs of Roseate Terns at nesting colonies in Massachusetts, 2010.

Buzzards Bay Project

The communities surrounding Buzzards Bay have a deep-rooted, sea-based heritage of which terns are a part. Terns benefit these communities and visitors to the area aesthetically, culturally and economically. The sights and sounds of summer seabirds greatly enrich the marine environment. Terns benefit fisherman directly because the presence of a flock of terns often signals the presence of commercially and recreationally important fish: large, predatory fish force smaller "forage" fish to the surface, where they are accessible to terns.

Through the early 1950s, up to 15,000 pairs of terns nested on four to five islands and fed throughout Buzzards Bay. By 1975 only 1,400 pairs remained, all at Bird Island. In addition to being displaced by gulls, terns were injured by exposure to PCBs from New Bedford Harbor , a Superfund site.

Intensive management at Bird Island (Marion) since the late-1960s, at Ram Island (Mattapoisett) since 1990 and at Penikese Island (Gosnold; one of the Elizabeth Islands) since 1998 has resulted in a gradual recovery of numbers to nearly 8,000 nesting pairs as of the 2010 nesting season (Figures 7 and 8). Funding to restore terns to the New Bedford Harbor environment has been provided by the New Bedford Harbor Trustee Council from 1999 to present. Management at Bird Island is conducted with the cooperation of the Town of Marion.

Figure 7.  Numbers of pairs of Common Terns at Bird, Ram, and Penikese Islands, Buzzards Bay, MA, 1970-2010.
Figure 7. Numbers of pairs of Common Terns at Bird, Ram, and Penikese Islands, Buzzards Bay, MA, 1970-2010.

 

Figure 8.  Numbers of pairs of Roseate Terns at Bird, Ram, and Penikese Islands, Buzzards Bay, MA, 1970-2010.
Figure 8. Numbers of pairs of Roseate Terns at Bird, Ram, and Penikese Islands, Buzzards Bay, MA, 1970-2010.

Because of terns' vulnerability to threats, populations in Buzzards Bay are managed aggressively in order to protect the improvements already achieved and extend restoration (Figure 9). Together, Bird, Ram, and Penikese Islands support nearly half the Roseate Terns in the endangered Northeast population (Figure 10). Therefore, protection and management of the terns and the islands is of critical importance. Each year, MassWildlife staff protects, manages, and monitors the terns on these islands to increase abundance, enhance productivity, and gauge progress towards recovery of the populations. Seasonal tern restoration job opportunities with MassWildlife's Natural Heritage & Endangered Species Program are available annually.

Figure 9.  Tern research at Penikese Island, MA.
Figure 9. Tern research at Penikese Island, MA.

 

Figure 10.  Number of pairs of Roseate Terns at major nesting colonies in the Northeast U.S., 2010.
Figure 10. Number of pairs of Roseate Terns at major nesting colonies in the Northeast U.S., 2010.

Projects to restore nesting habitat -- rapidly dwindling due to erosion and sea-level rise -- are underway at tiny Bird and Ram Islands (Fig. 11), which lie just a few feet above sea-level. At both sites, eroded areas will be filled with sand and gravel to create suitable tern nesting habitat. At Bird Island, a deteriorating seawall will be rebuilt to better protect the upland habitat.

Tern nesting habitat restoration on Ram Island
Figure 11. Tern nesting habitat restoration on Ram Island: (A) March 2010, before construction, and (B) July 2010, post-construction.

For more information about terns or the Buzzards Bay Tern Restoration project, contact Carolyn Mostello at Carolyn.mostello@state.ma.us.