Bobolinks

Bobolinks in field

NPS Photo / Gillian Audier

Length: 5.9-8.3 in (15-21 cm)
Weight: 1.0-2.0 oz (29-56 g)
Wingspan: 10.6 in (27 cm)

General Description

Bobolink (Dolichonyx oryzivorous) breeding males are mostly black with a white back and rump, complemented by a rich buffy nape. In contrast, females and nonbreeding males appear in warm buffy brown, streaked with dark brown on the back and flanks, featuring bold brown stripes on the crown and an unstreaked nape. Bobolinks have a pinkish bill.

Habitat

Bobolinks thrive in tall grasslands, uncut pastures, overgrown fields, meadows, and remaining prairies across the continent. During molting and migration, they can often be found in marshes and agricultural fields, especially rice fields.

Behavior

In spring, male bobolinks engage in conspicuous display flights over grasslands, fluttering their wings while singing. At other times, they remain hidden in tall grasses or brush, clinging to seed heads or foraging on the ground. Bobolinks often migrate in sizable flocks.

Diet

During the breeding season, bobolinks primarily consume weed seeds, insect larvae, adult insects, spiders, and other arachnids. In migration and winter, their diet shifts to wild and domesticated rice, oats, small grains, corn, weeds, and occasional insects.

Nesting

Females select nest sites on the ground within the male’s territory, usually on wet soil at the base of large nonwoody plants like meadow rue, golden alexander, or clover.

Eggs and Incubation

Bobolink eggs are typically pale bluish gray to reddish brown with irregular spots of brown and lavender. The female incubates 3-7 eggs for 11-14 days, after which the chicks remain for 10-11 days until fledging and joining the flock.

Migration Status

After breeding, bobolinks move to freshwater marshes and coastal areas to molt and initiate their migration to South America. Their main wintering grounds lie in the southern interior of South America, where they inhabit grasslands, marshes, rice, and sorghum fields.

Worldly Travelers

The bobolink is one of the world's most impressive songbird migrants, traveling approximately 12,500 miles (20,000 kilometers) each year to and from southern South America, which can amount to traveling around the circumference of the earth 4 to 5 times in its lifetime. Bobolinks can orient themselves using the earth's magnetic field due to iron oxide in their nasal cavity, and they also navigate using the starry night sky.

 

Bobolink Monitoring at Marsh-Billings-Rockefeller

Marsh-Billings-Rockefeller conducts annual bobolink monitoring in the Elm Lot on Mount Tom, an important breeding habitat and active hayfield, in accordance with park regulations. This monitoring helps determine when Bobolinks have fledged each year, indicating when it is safe to harvest the hay. To learn more about helping with annual bobolink monitoring, visit our Volunteers-in-Parks page!