Date of this Version
In 1998 we initiated a test of the concept that Bird Conservation Areas (BCA's) can maintain populations of breeding grassland birds. The underlying hypothesis is that large core areas of quality habitat (such as native prairie) that are surrounded by neutral habitats (such as small-grain fields), and that are isolated from hostile habitats (such as woody vegetation) will result in avian densities and reproductive rates sufficient to at least maintain population levels of breeding birds. This concept was proposed by the Midwest Working Group of Partners In Flight (e.g., Pashley and Fitzgerald 1996) and endorsed also by the Prairie Pothole Joint Venture of the North American Waterfowl Management Plan. This evaluation is being conducted in the northern tallgrass prairie, but the concept may be more generally applicable.
In 1999, we added 11 study plots in Sheyenne National Grassland in southeastern North Dakota to the existing 33 study plots in northwestern Minnesota. All study plots were assigned to one of four categories: 1) small core area surrounded by neutral landscape, 2) small core area surrounded by hostile landscape, 3) large core area surrounded by neutral landscape, and 4) large core area surrounded by hostile landscape. This year, four of the study plots could not be censused or nest-searched because prairies received prescribed burning. On each of the remaining 40 study plots we collected data on population density of breeding birds by censusing each plot twice during the field season. Data on nesting success, predation, and brood parasitism were obtained from a subset of 29 study plots. In addition, we color-banded birds on four of the study plots, focusing on Clay-colored Sparrow, Savannah Sparrow, and Bobolink. In 2001, we recorded 58 species on our census plots (compared with 41, 53, and 54 in 1998, 1999, and 2000 respectively), found 838 nests of 41 species (compared with 293 of 19 species, 793 of 34 species, and 679 of 39 species in 1998, 1999, and 2000), and color-banded 318 birds (compared with 263 and 334 in 1999 and 2000).