Avian density, diversity, and species richness in riparian corridors and shelterbelts of east-central Kansas.

Abstract

A comparison of bird diversity, density, and species richness, as well as vegetative structure, was made between single row shelterbelts and narrow riparian corridors in east-central Kansas in 1992 and 1993. Both habitat types were essentially linear wooded islands surrounded by grassland and agricultural fields. All study sites were located on two areas, Flint Hills National wildlife Refuge and Melvern Reservoir Wildlife Management Area. Bird censuses were conducted on 26 sites from 1 July to 1 August, 1992 and from 1 June to 20 June, 1993. Line transects were used to census birds. One transect was established along the edge of each study site, and all transects were walked once during each year of the study. Bird diversity was calculated for each habitat each year. Bird density and species richness were calculated for each transect, and statistical comparisons were made among habitats, areas, and years. Bird species were categorized into three guilds, based on migratory status, to test for homogeneity of species' distributions over four habitat-areas. Vegetation structure variables included percent tree canopy, tree density, diameter at breast height (DBH) , tree species richness, snag density, percent bare ground, percent forb cover, percent grass cover, and percent shrub cover. Vegetation variables were measured every 100 m along the transects used for bird censuses. Means for each vegetation variable were calculated for each transect, and statistical comparisons were made among habitats, areas, and years. A t-test indicated that bird diversity was higher in shelterbelts in 1992. Three-factor analysis of variance indicated that bird density was higher in riparian zones, on Melvern sites, and in 1993. Bird species richness was higher in riparian zones, on Melvern sites, and in 1992. There were no differences among habitats, areas, or years for tree density and DBH. Percent tree canopy was higher on Melvern sites and in 1992. Snag density was higher in 1992. Tree species richness was higher in riparian zones. Percent grass cover was higher on Melvern sites. Percent bare ground was higher at Flint Hills sites and in 1993. Percent grass cover was higher in riparian zones, on Melvern sites, and in 1992. Birds in each migratory guild were not distributed homogeneously among habitat-area types either in 1992 or 1993.