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Northern Harrier flying
Northern Harrier © Kyle Wilmarth

Important Bird Area: Stellwagen Bank

Map of the Stellwagen Bank IBA site

Nominated By

Chris Leahy


333,440 acres

Towns and Counties

Massachusetts Bay


national marine sanctuary

Major Habitats

offshore marine bank

Land Use

nature & wildlife conservation/land trust, hunting/fishing, fisheries/aquaculture, research

Serious Threats

overfishing, habitat conversion

IBA Criteria

  • Category 1: Sites important for long-term research and/or monitoring projects that contribute substantially to ornithology, bird conservation, and/or education.
  • Category 4: Sites containing assemblages of species characteristic of a representative, rare, threatened, or unique habitat within the state or region.
  • Category 5: Seabirds: The site regularly supports 300 or more pelagic seabirds and/or terns or 3,000 or more gulls at one time. A pelagic site is the actual location being used by seabirds (e.g., Stellwagen Bank) and not the location from which an observer counts seabirds (e.g., Provincetown). Smaller concentrations of less common gulls such as Laughing or Bonaparte's gullswill be considered. Human-made food sources for gulls such as landfills and sewage outflows will not be considered. The designation "seabirds" includes shearwaters, storm-petrels, fulmars, gannets, jaegers, and alcids.

Site Description

Stellwagen Bank is a glacial sand deposit rising from the seafloor at the eastern edge of Massachusetts Bay. Due to a variety of physical conditions-relative shallowness of the water, large tidal range, strong currents, seasonal turnover in conjunction with the presence of the bank itself-conditions allow circulation of nutrients into the sunlit upper reaches of the water column where they sustain an abundance of planktonic organisms. These in turn support an unusually rich and diverse community of fish, marine turtles, marine mammals, and birds. Stellwagen Bank and surrounding waters were designated as a national marine sanctuary under the jurisdiction of the US Department of Commerce. Because of its biological richness and its easy accessibility from ports on Massachusetts Bay, Stellwagen Bank is heavily visited by recreational and commercial fishers, whale watchers, and birdwatchers.

Current Conservation Status

Pressure on the once-rich fishery has been intense, especially in the decades of the 1960s to 1980s when fishing technology achieved a high degree of "efficiency." During this period, our local fisheries were severely depleted, but a slow recovery may be starting as a result of government imposition of strict catch and gear limitations. In addition to harvesting fish from the water column, commercial fishing operations involve bottom trawls, which effectively scrape the seabed repeatedly, severely impacting the benthic ecosystem. In addition to effects the of fishing, Stellwagen Bank and surrounding waters have been subjected to contamination by human waste, low-level radioactive materials, a wide range of industrial toxins, oil spills and bilge pumping, storm-water discharge, contaminated sediments, construction debris, derelict ships, and explosives. Additional exploitation, for sand and gravel mining, oil and gas development, and creation of artificial islands on which legal offshore gambling casinos could be built, continues to be proposed. Another issue that is probably growing rather than abating is marine recreation including boating, recreational fishing and whale watching. We know relatively little about the consequences of disturbance of marine organisms. But there is evidence, for example, that whales are sensitive to boat noise, and there are proven instances of boat collisions killing Northern Right Whales, whose entire global population is extremely endangered. This is of concern to bird conservationists since decline of pivotal taxa such as cetaceans or certain fish species could result, directly or indirectly, in the decline of bird populations.

Considering all the aforementioned factors, it is astonishing that Stellwagen Bank continues to support its present rich community of marine organisms, from countless invertebrate forms to great whales. It is important to acknowledge that the ecosystem survives in spite of rather than because of human intervention and that our ignorance of how this marine ecosystem works is so significant. Just as it seems surprising that marine life continues to survive in relative abundance on Stellwagen Bank, so we should not be surprised if in the future the system collapses from causes that we have been unable to predict.

Ornithological Significance

Roseate Terns are seen regularly especially in late summer when 40 to 50 birds have been recorded on several occasions; this represents a significant percentage of the Northeastern population of this federally endangered species. Common Terns occur frequently, especially in late summer. Arctic Terns have been recorded in summer; given the tiny Massachusetts breeding population, it is conceivable that Stellwagen Bank could be an important feeding area. Leach's Storm-Petrel are occasionally seen on Stellwagen Bank in summer; there is no way of knowing the origin of these birds, but if it were determined that the small Massachusetts breeding population used the site regularly as a feeding ground, this would be of conservation significance. The principal significance of Stellwagen Bank as an IBA is as a feeding ground for summering, wintering, and migratory seabirds. Numbers of birds present in any given year and season are directly correlated with the presence of key food species, especially the American sand lance. These numbers are subject to great fluctuations due to human as well as natural causes, but the historical record shows that Stellwagen Bank has been a hot spot of marine biotic diversity and abundance for at least several hundred years and quite probably much longer. Stellwagen Bank is one of only a few Massachusetts examples of a shallow marine bank supporting a rich invertebrate fauna that in turn is utilized by several different bird communities from the farthest reaches of the Atlantic ocean including species that breed in the Arctic (Northern Fulmar and alcids), the Antartctic (Wilson's Storm-Petrel), and the Eastern Atlantic (Cory's Shearwater), as well as species (including listed species) that nest along the Massachusetts coast. Because of its economic significance for fishing and whale watching, threats to its ecological health, and its status as a marine sanctuary, Stellwagen Bank has been the subject of numerous studies and will doubtless continue to be monitored in various ways. No systematic year-round studies of bird populations in relation to food sources have ever been done for the site, and there is no bird-monitoring protocol in place. Given the significance of the site, both are certainly desirable.

Other Flora or Fauna of Significance

Stellwagen Bank is a globally significant summer feeding ground for the Humpback Whale, endangered throughout its range, and may play an important role in the breeding cycle of the Northern Right Whale, perhaps the most severely endangered of all the great whale species. Other species of globally endangered whales that occur regularly or irregularly on Stellwagen Bank are the Blue Whale, Fin Whale, and Sei Whale. Five species of threatened or endangered sea turtles have also been recorded at the site, though the importance of Stellwagen Bank to their survival is still unclear.

Data Sources

Bird Observer records.