Bobolink  (Dolichonyx oryzivorus)

Classified as Least Concern (LC) on the IUCN Red List (1).

Considered to be one of the most striking passerines in North America (2), the adult male bobolink’s white upperparts and black breast have earned it the alternative name “skunk blackbird” (3). This dark-below, white-above plumage pattern is only exhibited by the male during the breeding season, and is unique among North American songbirds. Other distinctive features of the male’s appearance during breeding include a buffy-yellow patch at the back of the head and a black, glossy beak (2). Outside the breeding season, the male moults its distinctive plumage, replacing it with a winter plumage that resembles that of the adult female. This is uniform buff on the body and head with dark stripes on the back, rump, sides and head, and with a pale, horn-coloured bill (2) (3). In overall appearance, the bobolink resembles a large sparrow, with stiff tail feathers and a conspicuously elongated, curved hind claw. Only the male bobolink produces a song, which is long and complex and has been described as “a bubbling delirium of ecstatic music” (2).

The breeding range of the bobolink is located in North America and Canada, extending from British Columbia and Alberta in the west, to western Newfoundland in the east, and south as far as West Virginia. Isolated breeding populations also occur in central Washington, north-east Nevada, north Utah, east Arizona, Kansas and north-central Kentucky.

The bobolink undergoes an extensive annual migration to South America, passing through a wide range of countries including Mexico, Guatemala, Belize, Honduras, Costa Rica, Panama and the Galapagos Islands in the west, and the Bahamas, Puerto Rico, Trinidad and Tobago and Lesser Antilles in the east. The winter is spent within a more restricted range, extending from eastern Bolivia and south-west Brazil, south through Paraguay and north-east Argentina to Buenos Aires province (2).

Historically, the bobolink nested in the tall-grassland and mixed-grass prairieland of mid-western U.S.A and southern-central Canada. Following the wide-scale conversion of this habitat to agricultural land, the bobolink moved into the meadows and hay fields that were created as a result of forest clearance. After nesting, this species shelters in freshwater marshes and around coastal areas, where it completes moulting, before migrating to the expansive grasslands of central South America, where it overwinters (2).

After overwintering in the southern hemisphere, vast, generally single-sex, flocks of bobolinks undergo an approximately 10,000 kilometre journey—one of the longest migrations of all New World passerines—to the North American nesting grounds (2). In order to navigate across such a vast distance, the birds are believed to use the magnetic field of the Earth, as well as the positions of the stars. The journey begins in early Match and may take over two months to complete, with most individuals arriving at the nesting grounds in May (2) (3).

After arriving at the nesting grounds, male bobolinks establish territories, and begin to compete for the attention of the females, a process which involves song, ritualized display, fighting, and male-male chases (2). Interestingly, male bobolinks may form breeding pairs with up to four females simultaneously, a breeding arrangement known as polygyny. The offspring produced by each pairing are not, however, attended to by the male equally. Usually, the brood produced by the female with which the male first pairs is given the most attention, while feeding and defending of young at the other nests is carried out only when time and resources permit (2) (3). The feeding of the chicks is, however, frequently assisted by another adult, often a non-breeding bird, in a behaviour termed cooperative breeding (2). The nest, which is constructed by the female bobolink, consists of interwoven coarse grass and weed stems lined with finer grasses, placed at the bottom of a slight depression at the base of a clump of grass (2) (3). A clutch of three to seven eggs is laid, which is incubated for around 11 to 13 days. The adult and juvenile bobolinks leave the breeding grounds in late July to mid August, at which point the plumage is moulted and the birds form mixed-sex, gregarious groups that fly south to the wintering grounds (2).

During the breeding season the bobolink mainly feeds on seeds, as well as a variety of larval and adult insects and arachnids. While migrating and while at the South American wintering grounds, this species consumes wild and domesticated rice, oats, other small grains, seeds and occasional insects (2).

The bobolink is shot as an agricultural pest in southern U.S.A. and is also persecuted for the same reason at its wintering grounds in South America. It is also collected as food in Jamaica, and males are trapped and sold as cage birds in Argentina (2). Probably the greatest threat to this species, however, is habitat loss. Changing land use practices in North America are resulting in the decline of the meadows and hay fields in which the bobolink breeds (2), and in South America, the grasslands that support overwintering populations are being replaced by agricultural land (4). Nevertheless, while this has led to a contraction in the bobolink’s range, at the current time its population is large and does not appear to be suffering a major decline (2).

The bobolink is protected under the Migratory Bird Treaty Act, and also listed as a Species of Special Concern in some American states. It has been recommended that the meadows and fields that support nesting bobolinks be maintained by annual mowing, undertaken after the bobolink’s young have fledged. On a similar basis, prairies should also be managed by burns, either after nesting has taken place, or several weeks before the adults arrive at the nesting grounds in the spring (2).

The Nature Conservancy is helping to conserve this species by protecting the bobolink’s breeding areas and migration paths. Nevertheless, further protection of its austral wintering grounds would be beneficial to ensure that this remarkable bird remains abundant (4).

View information on this species at the UNEP World Conservation Monitoring Centre.

To learn more about the conservation of the bobolink visit:

• The Nature Conservancy:
  www.nature.org/animals/birds/animals/bobolink.html

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org