Breeding birds of a large-scale tallgrass prairie restoration in Iowa: monitoring abundance and frequency of occurrence

Little is known about avian response to habitat restoration, particularly for tallgrass prairies. Neal Smith National Wildlife Refuge, established in 1990, is one of the largest tallgrass prairie restorations of its kind, with land acquisition approved at 3504 ha. Point count surveys were conducted at Neal Smith National Wildlife Refuge from mid May through mid July, 1994-1998. Randomly selected points from four vegetation classes: cropland, herbaceous, riparian, and woodland, were surveyed over the five year study period. A total of 91 summer resident bird species were detected, including 8 grassland-specific species and 2 species from the Iowa threatened species list. We report results based upon trends in frequency of occurrence and relative abundance for 26 avian species considered characteristic of Iowa grassland and savanna communities. We detected significant increases in frequency of occurrence for 16 species, and corresponding significant increases in abundance for 6 of these species.;Several rare species and species of management concern were also observed. Riparian sites contained the highest species richness each year, while cropland sites contained lowest species richness and diversity each year. As Neal Smith National Wildlife Refuge continues efforts to plant and restore prairie and savanna, we expect to see a future increase in several grassland and savanna species that would not otherwise inhabit Iowa's agricultural landscape. Correlation analysis of our data indicates that, to maximize efficiency in monitoring populations over a large area, repeated sampling of points is unnecessary within a season. For continued long-term avian monitoring, we have also revised the point count methodology and included details pertaining to recommended changes and ideas for future avian research.