Goals & Methods

Tufted titmouse © Anne Greene
Tufted titmouse © Anne Greene

Mass Audubon has been carrying out extensive surveys of the birds that nest on our wildlife sanctuaries from 2004 to the present. The goals of these surveys are to:

  • Enhance our knowledge about the birds that nest on our wildlife sanctuaries, particularly those of conservation concern.
  • Use current distributions and abundances of breeding birds on our wildlife sanctuaries as a basis for comparison with any future changes.
  • Determine how representative our wildlife sanctuaries are of the Commonwealth as a whole in terms of breeding birds.

In addition, there are some interesting scientific questions that our surveys can address:

  • Do larger wildlife sanctuaries contain greater species richness and abundance of breeding birds, particularly those of conservation concern, than smaller wildlife sanctuaries?
  • Do wildlife sanctuaries with more acreage of contiguous forest contain greater numbers of breeding forest interior birds than those where the forest patches are small and interspersed with fields and shrublands?
  • How different are the avian communities of our eastern Massachusetts wildlife sanctuaries to from those of central and western Massachusetts.

Methods

We use the standard method of 10-minute point counts within a circle to survey breeding birds. Observers stand in the center of the circle and record all breeding birds seen or heard both within and outside the circle. How far they look depends on the type of natural community. Circles in forested and wooded swamp habitats are 164 ft (50 m) in radius; grassland and marsh circles are 328 ft (100 m) in radius.

The layout of circles depends to a large extent on the size of the wildlife sanctuary:

  • In larger wildlife sanctuaries (>500 acres), individual circles are located where they sample only one particular habitat type and are placed so that the edge of the circle is a minimum of 492 ft from habitat transition (e.g., the boundary between a field and a forest).
  • In smaller wildlife sanctuaries, finding large areas of one habitat type is impossible, so the circles encompass habitat transitions.
  • Whether the sanctuary is large or small, the edge of one circle is no closer than 656 ft from the edge of another circle to reduce the possibility of double counting any birds.

Counting by Mass Audubon staff and volunteers occurs between 5 and 10 AM from June 1 through July 4th. Observers make three visits to each circle during that time period. A number of our circles are visited by two observers who use a double observer protocol developed by the United States Geological Survey’s Patuxent Wildlife Research Center.

The goal is to sample each wildlife sanctuary at a minimum for three consecutive seasons over a 10 year cycle. Our methods work well for birds of forests and grasslands that are active during the day. However, certain groups of birds are not well sampled. These include nocturnal birds like owls and whip-poor-wills, and species that tend to be quiet and well hidden, such as rails. We plan to target those in future surveys.