Find a Bird - BBA1

May 21 to June 29

one or two

The deforested New England of the nineteenth century provided endless acres of suitable habitat for birds that nested in fields, meadows, and pastures, and the populations of species, such as the Savannah Sparrow, that preferred these habitats must have been legion. With the decline of agriculture in Massachusetts in the late nineteenth and throughout the twentieth century, those species that required open spaces became more and more limited to remnants of this once-expansive ecosystem as agrarian landscapes were gradually transformed into forests or suburban developments.

Today, the Savannah Sparrow is found most commonly as a breeding resident in coastal dunes and heaths, the edges of salt marshes, the farmlands of the Connecticut River valley, and the hillside pastures of the Berkshires. Elsewhere, Savannah Sparrows can be found on the grassy verges of airstrips and on the scattered, but ever fewer farms and pastures throughout the state.

Small numbers of Savannah Sparrows are found each winter in Massachusetts, especially along the coast and Islands, but the bulk of the New England population winters in the southeastern United States. Many leave for their northern breeding grounds long before the close of winter, with Massachusetts birds arriving during April. Savannah Sparrows are common migrants in Massachusetts during both spring and fall, a reflection of their widespread distribution and abundance in the northern United States and eastern Canada.

Both adults and immatures tend to return to the same breeding or natal site; males generally arrive first. Territories are staked out by patrolling males with frequent vocalizations—an insectlike buzzy song given by the male and a variety of calls given by both sexes in different contexts: agonistic, alarm, contact. Pairs are formed one to three weeks before the eggs are laid, but Savannah Sparrow males are not monogamous and up to 47 percent of some populations of males are mated to more than one female.

The female alone chooses the nest site and builds the nest, which consists of an exterior cup of coarse grasses and an inner lining of fine grasses. Only the female incubates the four to five pale-colored, speckled eggs that make up the usual clutch; hatching occurs in 12 days. Brooding of the nestlings is mostly by the female, but both the male and the female feed the young, which fledge in about 11 days. Both parents feed and care for the fledglings for about 14 days, at which time the female will often begin a second, and sometimes a third, clutch.

The juvenal plumage is worn only briefly before being replaced by the postjuvenal plumage, and both closely resemble the adult plumage. Following fledging, molting Savannah Sparrows tend to gather in loose flocks in favored habitats. They begin their south- ward migration in mid-September, reaching maximum abundance in October. Philopatry remains strong in the winter, and, in one instance, 40 percent of the adults returned to the same location where they had spent the previous winter.

Atlas 1 data collected from 1975-1979