Abstract

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Holler, J.I. 2000. Avian diversity, abundance and conservation on a large prairie landscape reserve in Northwestern Minnesota. M.S. Thesis, University of Minnesota. 108 pp.

Abstract:

Tallgrass prairie is one of the most endangered ecosystems in North America, the Midwest, and Minnesota, only 0.4 0.8% of Minnesota's native grassland remains in small, scattered patches. North American grassland associated bird species have also decreased in abundance, showing steeper and more widespread declines than any other group of birds. This study examined the potential contribution of a large (3,238 ha) native prairie landscape reserve (Rothsay Prairie Landscape Unit) in northwestern Minnesota to conservation of avian biodiversity. Objectives were to: 1) determine the distribution and abundance of bird species occurring on the Rothsay Prairie Landscape Unit (Rothsay Unit); 2) determine if there was an association between habitat structure, vegetative community type, or management regime and the presence of bird species using the area; and 3) identify management options to maximize abundance and distribution of prairie avifauna present in the study area, emphasizing species designated as Conservation Concern in Minnesota in 1989.

In May - July 1989, three minute point counts were repeated six times at 155 listening stations centered in 100 m fixed radius circular plots across the study area to determine bird presence and breeding status. Habitat data were also collected to examine the association between bird presence and habitat characteristics. ArcView? GIS software was employed to compare vegetative community types in each plot to the entire study area and to extrapolate Rothsay Unit community types to the remainder of reserve habitat in Northern Tallgrass Prairie Ecoregion.

During the1989 field season 11,631 bird observations of 76 different species were recorded on the study area. Fifty seven species (75%) were considered breeding birds on the Rothsay Unit, including 81% of 21 Conservation Concern Species. Two thirds (32) of the breeding species were grassland dependent species. Twenty seven breeding species (47%) were abundant or common. Breeding bird distribution ranged from six widely distributed (documented in > 100 plots), nine moderately distributed, 17 (30%) restricted, and 25 (44%) local species. The absolute and ecological density of breeding pairs ranged from 11 to 102 prs/km~ and 0.2 to 58 prs/km2, respectively.

The bird observation plots were a representative sample of the proportion of vegetative community types on the Rothsay Unit (X27= 5.0, p < 0.005). Results from a forward step wise multiple regression showed statistically significant linear associations between 16 bird species and a number of habitat variables. Grass height was associated with the most bird species (i.e., ten), followed by land use, which was associated with seven species. Tree cover was not associated positively or negatively with any species.

The Rothsay Unit, one of the largest contiguous areas of native prairie in Minnesota, has significance for conservation of native prairie/grassland avifauna and native prairie habitats in Minnesota and the ecoregion. To ensure future viability of the Rothsay Unit as a prairie landscape reserve for the conservation of native plant and bird communities, efforts should: include private stakeholders, occur at the regional/ ecosystem level, adopt an interdisciplinary approach for effective management, and explore expansion of the Rothsay Unit to create a larger prairie conservation area.

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