Status: Threatened (federally & provincially), since 2010.
Like many other bird species there is sexual dimorphism in colour (males and females look different). Breeding males are mostly black (head and underparts) with some white on their lower back/tail, and a prominent yellow patch on the back of their head/neck. Mature females are sparrow-like, light beige in colour with brown streaks, have yellowy upperparts and a prominent dark eye line. Out of breeding season, the male looks quite similar to the female, but are slightly darker from above. During migration and winter both sexes have a light pink bill, but the male’s bill turns black during breeding season. Juveniles resemble females without the streaking patterns.
The male flight song sounds like their name over and over (bobolink-bobolink-bobolink-bobolink) and is often described as “metallic-like” and kind of sounds like a robot. During migration they give a pink call. Listen to their songs here!
Bobolinks eat many different types of seeds and invertebrates off of the ground or in short vegetation. More than half of their diet consists of larval and adult insects, especially during their breeding season. Access to these insects is very important for reproduction because nestlings are fed only insects. During their migration Bobolinks diet shifts to being mainly seed based.
Habitat: Where do they live?
The Bobolink has a large breeding range, extending along the southern Canada from British Columbia to Newfoundland and Labrador, and throughout most of the United States, with higher concentrations in the northeastern states. About 28% of Bobolinks breed within Canada.
Bobolinks evolved to live in tallgrass prairies, but these ecosystems have declined to less than 1% of their historic range in Ontario. Since European settlement, Bobolinks and other grassland species have adapted to thrived in hayfields and pastures. Their abundance in Ontario is closely tied with the areas of low-intensity agriculture, such as Grey and Bruce Counties. Breeding Bobolinks have been seen across the range of the Land Between.
Hayfields are the Bobolink’s preferred habitat because they have plant cover at the start of their breeding season (unlike in most grain fields) which provides protection. They also occur in a range of open spaces with graminoids including peatlands, abandoned fields, and no-till cropland. Bobolinks tends to avoid crops in rows like corn, soybeans, and wheat, or intensively grazed pastures. Fluctuations in Bobolink abundance can be traced to changes in agricultural trends in producing hayfields and pasture, alfalfa, dairy, and row crops.
Nesting: Bobolinks have very specific nesting requirements: they like a leaf-litter layer, small shrubs to perch on, and tall grasses for cover. They will not nest in areas with too much bare soil, where shrubs are too dense, or where leaf-litter layer that is too deep. These characteristics are important because they do not nest in trees, but on the ground. Bobolinks apparently breed successfully in fragmented habitat fragments, but do not do well next to forest edges.
Migration: The Bobolink is a neotropical migrant - flying thousands of kilometers each year to overwinter in South America. The winter range of the Bobolink includes northeastern Argentina, eastern Uruguay, Paraguay, and southwestern Brazil. The range is predicted to expand as rice farms take up more land area in these regions.
Behaviour and Life Cycle:
Bobolinks return to Canada from May to early June. The males arrive a week earlier than the females and establishes its territory with courtship flights and songs. When the female arrives she builds a ground nest out of grasses and forbs in a shallow depression. After pairs are formed, eggs are laid one per day (up to 5 in Ontario). The female incubates the eggs for 12 days, and the young are then fed by both parents for about two weeks.
Males are territorial, and will chase away other grassland birds and some raptors before the hatching period. Their open ground nests are quite vulnerable to a range of predators including raptors, reptiles, and mammals. Feral domestic cats also prey on adults in some areas. Survival rates are fairly low, especially in hay fields that are harvested early.
They are an early fall migrant, and in mid- to late-July they form loose flocks to begin their southern journey. Bobolinks first head to eastern coastal habitat from New Jersey to Florida, until mid-September when they form large groups (up to 30,000) to continue southbound across the Caribbean.
Along with other grassland bird species in Southern Ontario, the Bobolink’s range grew with during colonization as forests were cleared for agriculture. However, their decline began in the 1980s as these fields went through natural succession, and land-use changes associated with urbanization occurred.
Current major threats to Ontario’s Bobolink populations are:
- Agricultural operations
- Associated with mortality, especially during the nesting season. Recent trends towards early haying (which can allow for two harvests) have been detrimental for Bobolinks.
- Loss of field habitat
- Happens as forage crops are converted to intensive grain, or are overgrown with trees.
- Habitat fragmentation
- Promotes a higher rate of predation on nests located near edges.
- Pesticide use on breeding and wintering grounds.
- Damages prey populations and may also have direct negative effects on Bobolinks
What conservation is occurring?
The vast majority of the Bobolink’s preferred habitat occurs on private agricultural land. Most habitat protection thus far has been through voluntary programs, private conservation groups, and the Permanent Cover Program (1989-1992) which restored unproductive grasslands in Canada. It has responded well to prairie restoration and agricultural land retirement programs.
How can we help?
Since most Bobolinks breed on private property the best thing we can do is to change the management regimes of grasslands. This includes encouraging farmers to wait until Bobolink breeding season is over to harvest hay. In addition, keeping cats indoors and only letting them outside on leashes will help to reduce predation. If you have open grass areas on your property consider leaving them uncut until breeding is complete in late July. Also avoid using pesticides on your property.
COSEWIC. 2010. COSEWIC assessment and status report on the Bobolink Dolichonyx oryzivorus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 42 pp. (www.sararegistry.gc.ca/status/status_e.cfm).
Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2005. Digital Distribution Maps of the Birds of the Western Hemisphere, version 2.1. NatureServe, Arlington, Virginia, USA.