Evaluation of the Bird Conservation Area Concept in the Northern Tallgrass Prairie Annual Report 2000

摘要

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 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. On each of the 44 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 2000, we recorded 54 species on our census plots (compared to 41 and 53 in 1998 and 1999, respectively), found 679 nests of 39 species (compared to 293 of 19 species, and 793 of 34 species in 1998 and 1999), and colorbanded 334 birds (compared to 263 in 1999).