Nesting in the prairies and cultivated land of south Canada and the northern United States, and wintering in the grasslands and marshes of Argentina, the bobolink migrates at least 5,000 miles each way. The vast distance is more impressive in relation to the bobolink’s diminutive size, averaging 7 inches in length, 11.5 inches in wingspan, and 1.5 ounces in weight.
Males are distinctive in their breeding plumage with a black and white rump and black and yellow nape, though their yellowish brown winter plumage is similar to the females'. In summer, bobolinks feed primarily on insects, switching to grain crops as they migrate south. The female builds the nest on the ground, in which she lays 5 to 6 eggs that incubate for about 13 days.
Bobolink numbers have been in decline since the middle of the 20th century, averaging a 3.8 percent decrease from 1980-1996. In North America, the loss of birds is mainly attributed to changes in land use, but it is suspected that winter survival is the main source of decline. The bobolink’s preferred natural grasslands are the main threatened habitat in Argentina, where very little of those important areas are formal protection. The bird is protected by the Migratory Bird Treaty Act in the US and Canada and is listed as a Species of Several Concern in several states. The Conservancy protects breeding areas and migration paths for the species.
April 05, 2011