Don't Fence Me In — Grassland Birds Need Space

It's said that trees and prairie birds don't mix. Now grassland bird expert Jim Herkert has the numbers to prove it. As science director for the Illinois Nature Conservancy, one of his primary recommendations is the removal of trees and bushes from grasslands that are important to birds. Trees harbor predators that prairie species can't handle. At the 375-acre Bartel Grassland, the Cook County Forest Preserve District last winter removed the nine miles of tree-rows (planted by farmers around their land) that had fragmented the preserve.

Herkert studied the bird life in the preserve's tree-row and grassland areas in 2001 and 2002 — the year before and the year after trees were removed. He found that numbers of the four most imperiled grassland birds on the site — Henslow's, grasshopper, and savanna sparrows as well as bobolinks — rose between 30 and 300 percent. Some other species of birds disappeared when the brush went, but these were mostly common species, like the crow and grackle, and all have vast habitat in the brushed-in former grasslands of other nearby preserves. The biggest increases in grassland birds were at the study points in the former brush-rows. Partners in the Bartel project include the Corporation for Open Lands, U.S. Army Corps of Engineers, and Audubon-Chicago Region.