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June 2000
We saw a lone bobolink in our yard this spring. He devoured dandelion seeds one evening and the next morning. Then he was gone. Returning to Maine from South America, the bobolink was using our yard as a refueling stop while traveling, we hoped, to join other bobolinks in suitable breeding habitat. Grassland birds, including bobolinks, are species that use old fields, upland meadows and pastures, wet meadows, or sandplain grasslands for breeding.
The history of grassland birds in Maine is intertwined with human history. Extensive forests grew up in Maine after the last glacial period ended ten thousand years ago. Except for scattered openings, natural permanent grasslands were unusual in the landscape. By the early 1700's, European settlers began to clear forests for farmland. By the 1800's, pastures and hayfields were common in the landscape and the populations of grassland bird species increased, possibly expansion of native populations and dispersal and colonization by more western populations.
With the Industrial Revolution in the 1860's, many people moved off the land and into cities. Farmland reverted to forest, and the open grasslands necessary to these species began to disappear. This trend continues today. Also, much farmland and other grasslands are being replaced by housing and business developments.
Changes in farming practices have also affected grassland bird species. Traditionally, haying of the farm fields was done late in the summer season. This allowed time for the grassland birds to nest and rear their young. Now, hay is mowed earlier, in late June and early July, and then mowed again in the summer. Mowing during the breeding period destroys adult birds and eggs or nestlings in their nests on the ground.
Between 1980 and 1996 in Maine, bobolink populations decreased 6.4% each year and eastern meadowlark populations decreased 7.1 % each year. In the Northeast, nine species of grassland birds are regionally threatened or endangered. Across the country, they are experiencing great population declines because of habitat loss. Overall, the greatest source of habitat loss for grassland birds in North America was the conversion of open prairie to till agriculture, and more recently, the conversion of pasture or hay fields to row crops. Similar land use conversions in South America also play an important role in declining populations.
Management practices for grassland bird species have been suggested for the Northeast. For technical assistance with these practices, landowners and land managers in Maine may contact the wildlife biologist in their regional office of the Dept. of Inland Fisheries and Wildlife. There are suggestions for managing grasslands that are mowed or grazed by livestock as well as grasslands at airfields and on capped landfills. The primary goals of the landowner, such as farm production, can be achieved while managing habitat for grassland birds.
When mowing hay is postponed until after August 1, species raising a second brood have time for the young to fledge in late July. If mowing is necessary before August 1, avoiding areas where birds are often seen or leaving small patches standing, perhaps at the edges or in strips, provides nesting sites. These small patches of standing grasses provide cover and feeding areas for grassland birds for the rest of the summer until they migrate. Fields not harvested for high quality hay can be maintained as fields by mowing every one to three years, in late August or September.
There is the opportunity to help grassland bird species survive by conserving their habitats and changing grassland management practices. Other bird species that depend on the insects and small mammals present in grassland habitats, such as American kestrels, northern harriers and red-tailed hawks, will be benefited as well. What we do makes a difference. In this case, the difference means life or death to grassland species.
By Nancy Coverstone (ncstone@umext.maine.edu), University of Maine Extension Educator in Androscoggin and Sagadahoc Counties
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