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Northern Harrier flying
Northern Harrier © Kyle Wilmarth

Massachusetts Important Bird Areas

An Important Bird Area (IBA) is a site providing essential habitat to one or more species of breeding, wintering, and/or migrating birds. IBAs generally support high-priority species, large concentrations of birds, exceptional bird habitat, and/or have substantial research or educational value.

The primary goals of the IBA Program are:

  • To identify, nominate, and designate key sites that contribute to the preservation of significant bird populations or communities.
  • To provide information that will help land managers evaluate areas for habitat management and/or land acquisition.
  • To activate public and private participation in bird conservation efforts.
  • To provide public education and community outreach opportunities.

IBA Criteria Categories

Sites regularly holding significant numbers of an endangered, threatened, vulnerable, or declining species.

Sites that regularly support significant numbers of one or more of the following breeding or nonbreeding species listed as endangered, threatened, or of special concern in the state of Massachusetts. These include breeding, wintering, or migratory areas. The site should be one of regular and/or recent occurrence (in the past ten years). Thresholds will vary and may include sites with 1% of the state population (if known) in a season or represent one of the three to five sites in the state with the highest regularly occurring numbers. The site holds a significant number of individuals classified as:

Federally Endangered or Threatened

(1% or more of state population)
Endangered - Roseate Tern
Threatened - Bald Eagle & Piping Plover
Delisted - Peregrine Falcon

State-Endangered, Threatened, or of Special Concern

(1% or more of state population)

Sites regularly holding significant numbers of species of high conservation priority in Massachusetts.

Sites that regularly support significant breeding or nonbreeding densities of the following species identified as high conservation priorities by Partners in Flight (excluding state-listed species already mentioned above). Thresholds will vary but may include sites with 25 or more breeding pairs, 5% or more of the state population (if known), or the two to three sites in the state containing the highest regularly occurring numbers. May also include sites with significant complements of species.

High Conservation Priority Species

Species were chosen for the following reasons:

  • They are of conservation concern throughout their range and show high vulnerability in a number of factors.
  • They are of moderate continental priority but are important to consider for conservation within a region.
  • They are on the U.S. National Watch List.

Sites where birds concentrate in significant numbers in the breeding season, in winter, or during migration.

Sites that regularly support significant numbers of one or more species during the breeding, nonbreeding, or migration seasons. Except where indicated, numerical estimates should be based on a short period of time, e.g., one-time counts such as daily surveys—not on cumulative totals. Introduced and feral species should not be counted.

The numerical criteria categories below are guidelines only. Other factors, such as the quality and location of habitat, along with the distribution and importance of species, may also be considered. Lower numbers will be considered for inland sites where, with species such as waterfowl, concentrations are smaller but are regionally significant.


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 gulls will 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.

Wading Birds

The site regularly supports 25 or more breeding pairs of wading birds or 100 or more foraging individuals (at one time) during migration. The designation "wading birds" includes bitterns, herons, egrets, and ibises.


The site regularly supports 500 or more waterfowl at any one time. The designation "waterfowl" includes birds such as loons, grebes, cormorants, geese, ducks, coots, and moorhens.


The site is a bottleneck or migration corridor for more than 5,000 migratory raptors during a migration season.


The site regularly supports 1,000 or more shorebirds at one time at a coastal site, during some part of the year, or a significant concentration of shorebirds at one time at a nontidal site. The designation "shorebirds" includes birds such as plovers, sandpipers, snipe, woodcocks, and phalaropes.

Land Birds

The site is an important migratory stopover or seasonal concentration site for migratory land birds (e.g., warblers). Sites may also qualify on the basis of supporting exceptionally high densities of breeding species as shown from point counts or other surveys or if they represent "migrant traps" relative to surrounding areas. Strong consideration will be given to areas with consistently high overall species diversity.

Single-species Concentrations

The site regularly supports significant concentrations of a flocking species but may not meet the thresholds above. The site should support a higher proportion of a species' statewide population (more than 1%, if known) than other similar sites.

Sites containing assemblages of species characteristic of a representative, rare, threatened, or unique habitat within the state or region.

This category is meant to cover relatively large areas capable of supporting significant bird populations, especially of species with specialized habitat types and requirements. Selection of sites will be based on avian assemblages within the habitat community type, not on the habitat community type alone. Therefore, whenever possible, characteristic species of birds indicative of the habitat type should be identified and quantified.

Major avian habitat types and categories in Massachusetts

  • Spruce/Fir forest
  • Northern hardwood forest
  • Oak/conifer transitional forest (Red Oak, Eastern Hemlock, White Pine, etc.)
  • Pitch Pine/Scrub Oak forest
  • Early successional shrubland
  • Cultural grassland
  • Cultivated field
  • Emergent freshwater wetland (i.e. cattail marsh)
  • Peatlands (bogs and fens)
  • Maritime heathland /sandplain grassland
  • Palustrine wooded swamp (White Cedar, Red Maple, or floodplain)
  • Shrub/scrub wetland
  • Saltmarsh
  • Coastal beach/dune/island
  • Marine
  • River/stream
  • Lake/pond
  • Urban/suburban

Sites important for long-term research and/or monitoring projects that contribute substantially to ornithology, bird conservation, and/or education.

These are generally sites with a distinguished record and/or unique potential for long-term monitoring, or that possess exceptional educational value. Such sites may occur within urban, suburban, or rural settings. Evidence should be cited documenting the area’s value, such as through publications of research conducted at the site, or reports/evaluations for nonacademic educational facilities. Insofar as these sites are not necessarily essential habitats for birds, they are technically not Important Bird Areas, but they are nevertheless considered important to identify and conserve.

Additional Information on IBA Sites

Sites may be protected or unprotected, public or private. The sites may vary in size but are usually discrete and distinguishable in character, habitat, or ornithological importance from surrounding areas. Site boundaries may be either natural (e.g., rivers, watersheds) or human-made (e.g., roads, property boundaries). In general, an IBA should exist as an actual or potential protected area or should have the potential to be specifically managed for bird conservation.

An IBA, whenever possible, should be large enough to supply all or most of the needs of birds during the season for which the IBA is important. Not all IBAs can or will meet this last definition—for example, "flyover" sites for raptors.

A site that meets any one of the criteria in the five categories listed above may qualify as an Important Bird Area—some sites may meet several criteria. These criteria should not be considered absolute; other factors, such as relative importance compared to other sites, may be considered when making the final site selections.

Category 5 (Important Bird Research Areas) is included to cover sites that are important to bird conservation because of the research done there.