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Northern Harrier flying
Northern Harrier © Kyle Wilmarth

Important Bird Area: Bull Hill Fields

Map of Bull Hill Fields IBA site

Nominated By

Dottie Case


150 acres

Towns and Counties

Sunderland; Franklin


Delta Materials Corporation

Major Habitats

2% early successional shrubland, 50% cultivated field, 48% uncultivated field

Land Use

hunting/fishing, other recreation (ORVs), agriculture/livestock, quarry/gravel pit, suburban/residential, urban/industrial/commercial, undeveloped

Serious Threats

non-native invasive plants, pesticides (herbicides), extraction industry (gravel pit), habitat conversion, residential/commercial devel., disturbance to birds or habitat

Minor Threats


IBA Criteria

  • Category 1: Sites containing assemblages of species characteristic of a representative, rare, threatened, or unique habitat within the state or region.
  • Category 2: 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..
  • Category 4: Sites regularly holding significant numbers of species of high conservation priority in Massachusetts.

Site Description

The fields are chiefly agricultural with some sections typically allowed to go fallow for several years. On the north side of the plateaulike fields is the southern edge of the Mount Toby range-an area of various-sized hills culminating in the 1,200-foot summit. The woodlands (mixed, deciduous, and pine) end abruptly with rocky cliffs, which host raven nests and one endangered snake. A road intersects the fields, north of which are a few houses, tobacco barns, a waterfall, a pond, and a streambed. To the east lie woodlands, dry fields, and a gravel pit area. On the southern edge are federal, state, and private fish hatcheries. To the west is the town of Sunderland on the banks of the Connecticut River.

Current Conservation Status

Although the Bull Hill Fields currently have little or no legal protection, they are definitely worth protecting due to the presence of rare or unusual nesting birds. The mix of habitats within a relatively small area, so close to developed areas, as well as the immediate threat created by the adjacent gravel pit make it urgent to focus attention on this area.

Ornithological Significance

The Bull Hill fields offer a wide range of habitat needs for a variety of species at all seasons of the year, including a variety of food types for open country species, water in two nearby streams and small ponds, and shelter provided by shrubs along bordering fencerows. Due to its proximity to the Connecticut River, many migrants pass through this area. During spring migration, many northbound migrants have been observed pausing in the fields before journeying over the mountains. Fall hawk migration is extensive; hawks kettle and hang up in the wind currents over the cliffs. Many remain several weeks to rest and hunt in the fields. For more terrestrial individuals such as turkey and grouse, the fields become a greenbelt corridor to connect to lower areas that ultimately lead down to the river. This makes the site a boon to other wandering animals and butterflies, as well.

Other Flora or Fauna of Significance

Black (or Eastern) Rat Snake - Endangered in Massachusetts (mostly north side)

Jefferson's Salamander - of Special Concern in Massachusetts (north side pond)

Rare plants - North of Mount Toby foothills

Data Sources

D. Case, personal observations