Breeding Bird Atlas 2 Species Accounts
- Local and strongly increasing
Long reviled as dirty and gluttonous birds, Double-crested Cormorants were persecuted to the point of extirpation from the Commonwealth in the nineteenth century. Never a bird to be kept down, however, Double-crested Cormorants returned to Massachusetts in the 1940s and have since reestablished themselves as a breeding species. Cormorants are adroit swimmers and masterful divers, pursuing fish below the surface with great speed and agility. They nest on rocky offshore islands, either directly on the ground, in dead or live trees, and even on human-made structures.
Historic StatusNot to be mistaken for their larger winter counterparts, the Great Cormorant, Double-crested Cormorants spent many years seemingly avoiding Massachusetts. Extirpated as supposed fisheries pests, for many years they nested as nearby as Maine, only passing along the coast of the Bay State high in the sky in V-formations during migration. The demographic history of the Double-crested Cormorant in the twentieth century was marked by a growth spurt from the 1920s to the 1950s in the wake of the Migratory Bird Treaty Act of 1918; a midcentury decline resulting from increased pesticide usage; and a recovery following the 1970s (Hatch & Weselow 1999). By the early 1980s, the Massachusetts population had grown to 5,173 nesting pairs (Hatch 1982).
Atlas 1 DistributionLike so many other colonial piscivorous species in Massachusetts, Double-crested Cormorants were entirely restricted to coastal areas during Atlas 1. The recovering population had not yet reached any inland locales, preferring to locate their vulnerable colonies on rocky offshore islands well out of reach of humans and other mammalian predators. Atlas 1 colonies were concentrated mostly along the North Shore of the Coastal Plains, close to apparent source populations in northern New England. A few colonies were also known to exist on the Harbor Islands of the Boston Basin, and one colony was recorded on the Weepecket Islands in the Cape Cod and Islands region. Since Double-crested Cormorants were no longer legally persecuted and shot as pests and threats to public health, they soon began to expand following the solid foothold initiated in the 1940s.
Atlas 2 Distribution and ChangeThe slow but steady growth of the Double-crested Cormorant as a breeder in Massachusetts continued in the inter-Atlas years, and also included a surprising twist. Not content to just breed along the coast, the species moved inland, and was Confirmed as far west as Franklin County, in addition to being noted during the breeding season in the Marble Valleys. The species also strengthened its foothold around the Boston Harbor area; reached the South Coast, Nantucket, and Martha’s Vineyard; and sporadically injected itself into the Lower Worcester Plateau, the Southern New England Coastal Plains, and the Bristol/Narragansett Lowlands.
Atlas 1 Map
Atlas 2 Map
Atlas Change Map
|Atlas 1||Atlas 2||Change|
|Ecoregion||# Blocks||% Blocks||% of Range||# Blocks||% Blocks||% of Range||Change in # Blocks||Change in % Blocks|
|Marble Valleys/Housatonic Valley||0||0.0||0.0||1||2.6||1.3||1||2.6|
|Lower Berkshire Hills||0||0.0||0.0||0||0.0||0.0||0||0.0|
|Connecticut River Valley||0||0.0||0.0||4||6.2||5.2||4||8.3|
|Lower Worcester Plateau||0||0.0||0.0||1||1.3||1.3||1||1.9|
|S. New England Coastal Plains and Hills||5||1.9||55.6||25||8.8||32.5||17||7.5|
|Bristol and Narragansett Lowlands||0||0.0||0.0||19||16.7||24.7||17||16.8|
|Cape Cod and Islands||1||0.7||11.1||13||9.0||16.9||11||9.2|