Most Bobolinks begin their autumn migration by moving eastward toward the southeastern Atlantic Coast, even those from the western parts of the breeding range (southern British Columbia and eastern Oregon and Washington). Then they rest and accumulate fat before the long passage across the Caribbean to South America. Some apparently take a more direct route south from their northeastern summer homes and fly away from the coast over the Atlantic; there are numerous records of Bobolinks migrating south over Bermuda. Migrating bobolinks descend on rice fields and consume the crops; in past centuries, those who viewed them as agricultural pests shot them by the thousands and sold at market as “reed birds” or “butter birds.”

Northbound migration begins in March as the Bobolinks retrace their southbound route, with a more westerly trend. The older, more experienced males arrive first and begin defending the choicest territories in moist meadows, hayfields and grassy prairies. The male performs circling song flights over the fields with head held high, tail and rapidly fluttering wings held low, and the white feathers of the rump and epaulets displayed. Their excited jumbled and bubbling song is described in William Cullen Bryant’s poem “Robert of Lincoln,” as an onomatopoeic "Bob-o’-link, bob-o’-link, spink, spank, spink.” Older males sing a version of the song that is peculiar to their locality, which younger males learn from them, indicating that males return to the same sites year after year.

Bobolinks are often polygamous. As many as 30 percent of males have more than one mate; those most likely to win more than one female are more experienced and have the best territories. Females can be promiscuous as well. About 15 percent of nests contain nestlings sired by males other than the female’s social mate. The nest is placed in a small hollow on the ground. The female incubates the five or six speckled eggs in a cup of grass and weed stems. A significant number of Bobolink nests have “helpers,” apparently unmated males and females who contribute to the care of the young. Helpers are very unusual in species that migrate. Nestlings are fed insects, including caterpillars and grasshoppers. They leave the nest before they can fly. After the nesting season, the adults move into marshes to molt into winter plumage before embarking on migration.

Description:

Bobolinks are small, short-tailed blackbirds with short, conical bills. The male’s breeding plumage is unique: black underparts and face, with white on the rump and lower back. There are large white patches at the shoulders and buffy yellow on the back of the head and nape. The tail is black with sharply pointed feathers. Wings are black, showing buffy feather edges in fresh plumage. The bill is black during the breeding season and pinkish during the rest of the year. Males molt into a female-like plumage after the nesting season.

Females are cryptically colored with striped head and streaked upperparts. The underparts are plain buff with darker streaks at the flanks. The large size, prominent pale central crown stripe, and pink bill of the female is useful in distinguishing it from similar plain-breasted sparrows. Female Rose-breasted and Black-headed grosbeaks share the streaked upperparts and are approximately the same size, but usually occur in very different habitats and have much larger bills.

Recording credits:
Bobolink recorded by Gregory F. Budney and can be found on Eastern/Central Bird Songs.