Boston Harbor Islands National Recreation Area Coastal Breeding Bird Monitoring: 2009 Field Season Summary

Trocki, Carol

In 2002, Boston Harbor Islands National Recreation Area (BOHA; Figure 1), was designated as a Massachusetts Important Bird Area (IBA) because the islands provide habitat for a significant number of colonial-nesting waterbirds, including Least Terns (Sterna antillarum) and Common Terns (Sterna hirundo), which are both listed as species of special concern in the State of Massachusetts (Massachusetts Natural Heritage and Endangered Species Program 2007). BOHA also provides habitat for breeding wading birds including Snowy Egrets (Egretta thula) and Black-crowned Night-Herons (Nycticorax nycticorax) which are, respectively, species of high and moderate continental conservation concern (Kushlan et al. 2002). American Oystercatchers (Haematopus palliates) have expanded their range northward into Massachusetts and now have a substantial breeding population in the Boston Harbor Islands (Paton et al. 2005). The North American population of American Oystercatchers is listed as a high priority shorebird species with high conservation concern in the U.S. Shorebird Conservation Plan (2004). In addition, eiders, cormorants, several other wading and shorebird species, and gulls regularly nest on the islands.Much is known about the spatial distribution and abundance of breeding birds in Massachusetts (Veit and Petersen 1993), but less has been published on the avifauna of the Boston Harbor Islands. Although not part of a consistent monitoring program, periodic records of breeding waterbirds on the islands do exist (see Andrews 1990, Hatch 1984, Blodget and Livingston 1996, Parsons et al. 2001, Hatch 2001 and Nove 2001).In 2001-2003, Paton et al. (2005) conducted an avian inventory of BOHA, which in part established the need for long-term coastal breeding bird monitoring in the park. When compared with previous studies, the Paton et al. (2005) waterbird inventory suggested that:• Common Eiders have a small, but established colony of approximately 70 nests on islands in the Outer Harbor, primarily Calf Island.• Double-crested Cormorants have redistributed themselves among the islands of the Outer Harbor, but have maintained fairly stable numbers since the 1980s (Andrews 1990, Hatch 1984).• Wading birds have experienced a significant decline on Sarah Island where the population declined from 725 nests in 1994 (Parsons et al. 2001) to 112 nests in 2003. The number of nesting wading birds on Middle Brewster Island has varied from 124 nests in 1984-85 (Andrews 1990), to 207 nests in 1994 (Blodget and Livingston 1996), to only 14 pairs present in 2003. Wading birds are no longer present on Spectacle, Peddocks, or Gallops (Nove 2001).• American Oystercatchers have increased from only several pairs in the early 1990s (Veit and Petersen 1993; Nove 2001) to approximately 16 pairs on 14 islands in 2003.• Herring Gulls (Larus argentatus) have declined in BOHA (Andrews 1990), as they have regionally (Rome and Ellis 2004), which may be due in part to the restoration of Spectacle Island, a former landfill and gull nesting site.• Great Black-backed Gulls (Larus marinus) have maintained a stable population in BOHA (Andrews 1990), though regional data suggests they may be increasing (Rome and Ellis 2004). • Least Terns have a small but relatively stable population (< 100 pairs), usually on Rainsford or Lovell’s Islands (Hatch 2001, Nove 2001).• Common Terns have declined from a peak of 100 pairs in 1993 (Hatch 2001) to approximately a dozen pairs on Snake Island in 2003.

Boston Harbor Islands National Recreation Area Coastal Breeding Bird Monitoring: 2009 Field Season Summary

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