Breeding Bird Atlas 1 Species Accounts
Number of Broods
Furthermore, the reforestation of the cleared land of a century ago has significantly impacted nesting habitat. There has also been a reduction of the Bobolink’s preferred habitat of tall hay fields and upland meadows due to suburban development and a decreasing demand for hay. Even in the few appropriate nesting areas that remain, the grass is often cut in June before the birds have completed nesting.
During the Atlas period, the Bobolink was widespread in central and western sections of the state and in Essex County. It was much scarcer to the southeast, was not confirmed nesting on Cape Cod or Martha’s Vineyard, and was recorded as a possible breeder from only one block on Nantucket. Bobolinks are now most commonly seen as they migrate through in the spring or fall. They arrive in May, and a few settle in favorable areas to attempt nesting. Flocks of males appear first and sing from fields and meadows. The song is a rolling series of clear, short notes that rise higher and higher in pitch. Heard from a distance, a flock’s songs sound like a pleasing chorus of musical, burbling notes.
Males sing in flight or while perched in trees or on the tops of weed stalks. Frequently, the singing is accompanied by a posturing display; the male’s buff nape feathers are ruffled, his tail is spread, and his wings are partly opened. Often, the males will launch themselves high into the air while singing and then flutter downward. Males display to other males and to the females who arrive slightly later. During courtship, males chase females, sometimes pausing to do their song-flight display. The common call note is a sharp quink. When alarmed, females give a call that sounds like quick, and the males produce a somewhat lower pitched chow. Young call for food with a chib note.
Bobolinks are gregarious and flock for most of the year. They are territorial only during mating and the early part of the nesting period. After the young hatch, there is little, if any, territorial defense. Evidence indicates that these birds can be polygamous, with a male paired to more than one female.
The nest, built by the female, is well concealed in tall grass and difficult to locate. It is usually on the ground in a hollow depression or clump of weeds and is a loosely constructed cup of coarse grasses or weak stems lined with finer grasses. Two state nests were on the ground in fields of tall grasses and vetch (CNR). From four to seven eggs are laid, with an average clutch being five or six. The clutch sizes for 3 Massachusetts nests were four eggs (1 nest), five eggs (2 nests) (DKW). Eggs are gray or a pale cinnamon color with irregular splotches of brown or lavender clustered at the larger end. Incubation by the female lasts from 10 to 14 days. The female may sit tight on the nest and flush only at the last minute when she is approached, or she may run for some distance among the grasses before taking flight. The male keeps alert for any danger to the nest.
For several days after hatching, the young remain huddled in the nest, their coloring making them almost indistinguishable from the surrounding vegetation. At about 10 or 11 days of age, they may crawl away from the nest and, scattered, remain hidden in the tall grass. They are unable to fly until they are 10 to 14 days old. Both parents feed the young. Data on Massachusetts nests is scanty. Nestlings have been observed in the state from June 18 to June 20 (BOEM, CNR). A nest in Hamilton contained six young a few days old on June 18, and a Rowley nest held four young on June 20 (CNR). Fledged young have been recorded in the Commonwealth from late June to mid-July (BOEM, TC, Meservey). One brood is raised in a season.
In late July, after the young have become independent and males have ceased singing, Bobolinks gather in marshes and become inconspicuous during the molting season. They feed on weed seeds, wild oats, and rice. Migration begins in July and continues throughout August to late September. While they are migrating at night, their characteristic quink note can be heard as they pass overhead. Bobolinks winter in central and southern South America.