FAYETTEVILLE, Ark. - As America’s grasslands have been replaced by wheat and corn fields, the songs of grassland birds have dwindled and all but disappeared from the landscape. A new study shows that a government program - if properly implemented - may be helping to restore these native birds to habitats.

Douglas Johnson and Lawrence Igl of the Northern Prairie Wildlife Research Center in Jamestown, N.D. report their findings in the most recent issue of The Auk, published by the American Ornithological Union and edited by Kimberly Smith, professor of biological sciences at the University of Arkansas.

This is the first study that examines the influence on bird populations of the Conservation Reserve Program (CRP), a U.S. government program designed to retire crop land and re-plant it with prairie species for at least 10 years. About 13.7 million hecatres had been restored to grassland by the year 2000. However, the grassland has been restored in small patches, scattered about the plains, causing habitat fragmentation that may cause trouble for some species.

Their results indicate that putting a CRP field near existing grassland or establishing one large CRP field rather than several small ones would benefit more grassland bird species.

In one of the most comprehensive studies of its kind, the researchers studied the abundance of 15 grassland bird species at 303 sites distributed between nine different counties in Montana, North Dakota, South Dakota and Minnesota. They found that most of the species examined displayed variable sensitivity to habitat size.

Some birds, like northern harriers and clay-colored sparrows, favored larger grassland areas. Other species, like the common yellowthroat and the red-winged blackbird, seemed to select habitat features, such as wet areas or fencerows, over habitat size.

Two of the birds studied, the mourning dove and the brown-headed cowbird, were more common in smaller grassland patches, possibly because they prefer the edge habitat, the researchers contend.

The bird’s habitat selection also varied between the same species at different sites, emphasizing the need for comprehensive, multiple study sites to get a comprehensive ecological picture, the researchers said.

In an accompanying overview published in The Auk, Peter Vickery of the Massachusetts Audubon Society and James Herkert of the Illinois Endangered Species and Protection Board put those results into a broader perspective for North America. Over the last 30 years, populations of 13 grassland bird species have exhibited significant declines. These declines appear to be due to grassland habitat loss, the researchers contend.

Although the Conservation Reserve Program has restored some 13.7 heactres of grassland habitat, the researchers point out that nearly 10.5 million heacatres of pasture and range land were lost between 1982 and 1997. They also note that most of the contracts for CRP fields involve small tracts of land, which most of the declining bird species tend not to use.

Editor’s note: Kimberly Smith, professor of biological sciences at the University of Arkansas, is the editor of the Auk. For more information or for a copy of the manuscript or overview article, please contact him at the e-mail addresses or number above.