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Bobolink

Male Bobolink perched on vegetation
Male Bobolink. Photo by Gordon Ellmers

Dolichonyx oryzivorus

New York Status: Not Listed

Federal Status: Not Listed

Description

Breeding males of this grassland bird species have both a unique appearance and song. Their underside is completely black and they have a buff-colored "cap" of feathers on their head, while females, juveniles and non-breeding males are yellow/buff underneath with brown wings and tails. The male's song, which is given in flight, is cheerful or "jangling" and can contain anywhere from 25-50 notes. Bobolinks are medium-sized songbirds with a short, conical bill (total body length is15.2-20.5 cm; males weigh between 34-56 g and females weigh 29-49 g).

Life History

Their diet consists of insects, seeds and grains. Bobolinks build their nests on the ground in small depressions out of dead grasses and weeds, and lay a clutch of 1-7 eggs per nest. They may re-nest if their first attempt was unsuccessful. Male Bobolinks are polygamous, and may nest with more than one female at once within his territory. Bobolinks begin breeding around 2 years of age and may breed every year. They are territorial during the breeding season, but form large flocks during migration remain in flocks over the winter. They often return to the same breeding grounds each year.

Bobolink range map
Bobolink Range


Distribution and Habitat

Bobolinks breed across their range in North America, from British Columbia east to Newfoundland, and as far south as West Virginia. A few small isolated pockets remain as far south as Arizona. It is believed that they originally occupied only the mid-west, but expanded both west and eastward as forests were cleared. Bobolinks begin nesting around mid-May in New York in large, open grasslands or former hayfields containing a mixture of medium-tall grasses and forbs with few shrubs or trees. They prefer fields with 3-4 cm of thatch on the ground. The minimum field size needed for successful breeding is 5-10 acres, but larger fields are preferred and can support more breeding pairs. They overwinter in the pampas region of South America, in Argentina and Brazil. This 12,000 mile round-trip migration is one of the longest made by a songbird in the Western Hemisphere.

Status

Although still fairly common across the US, Bobolink numbers have decreased by 2% per year across North America since 1966. Declines can be attributed to farm abandonment and modern hay practices of more frequent and early cutting. In New York, the main cause of nest failure is cutting for hay during the nesting season. In addition, Bobolinks are persecuted as agricultural pests in their wintering range.




Management and Research Needs

Bobolink distribution in New York 1985

Bobolink distribution in New York in 2005
Distribution of Bobolink in New York from 1st and 2nd Breeding Bird Atlas Records

Several actions may be taken to help prevent a further decline in their numbers. To maintain grasslands, fields should be cut every few years to avoid vegetative succession towards trees and shrubs that will cause the habitat to become unsuitable for Bobolinks. Delayed cutting of hayfields until after the chicks have fledged (after August 1st ) is best. If this is not an option then mowing from inside out may provide an escape route for adult birds and older fledglings. For more information on how to help grasslands birds, please refer to these Best Management Practices (BMP's).


Little is known about their migratory patterns and behaviors. Future research should concentrate on their migration and on their wintering grounds in South America. Over-persecution may be causing population declines, in concert with habitat destruction.

Additional References

Bollinger, E. K. and T. A. Gavin. 1992. Eastern Bobolink populations: ecology and conservation in an agricultural landscape. Pages 497-506 in Ecology and conservation of neotropical migrant landbirds. (Hagan III, J. M. and D. W. Johnston, Eds.) Smithson. Inst. Press, Washington, D.C.


Martin, S. G., and T. A. Gavin. 1995. Bobolink (Dolichonyx oryzivorus). In The Birds of North America, No. 176 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.