AVIAN DIVERSITY IN MANAGED LANDSCAPES IN THE OAK OPENINGS REGION
The Oak Openings habitat is the sole remaining patch of a once larger biome of the lower Great Lakes system. Prior to European settlement, the Oak Openings was a pocket of prairie and oak savanna nearly surrounded by the forests of the Great Black Swamp.
Four habitats have been investigated at the Ostrich Lane site since 1993 as part of ongoing research of the Oak Openings region and in conjunction with the MAPS program. Degraded grassland (shrub/scrub), grassland, managed oak savanna, and unmanaged oak woodland each have four nets placed and monitored once every 10 days from early June to mid August. Data collected on captured birds includes species, age, sex, fat condition, mass, molt, breeding status, time, and net of capture. Banding effort is conducted for six hours each sample day.
Prior to the 1994 breeding season the grassland was cleared of all woody vegetation. It was mowed during the fall of 1995 and burned in the springs of 1996 and 1997 to maintain its openness. The managed oak savanna was burned in the spring of 1994, 1995, 1998, and 1999. The scrub/shrub was partially cleared in 1994, 1999 and 2003.
Species richness and bird abundance was compared between the four habitats. The scrub/shrub habitat indicated the greatest richness and abundance followed by the grassland, unburned oak woodland, and the managed oak savanna with the lowest richness and abundance. Each species was assigned to one of four community categories. These were woodland, grassland, shrub, and generalist. Grassland specialists were captured only in the grassland habitat while generalist made up the greatest component of richness for each habitat. The generalist also made up the greatest proportion of bird abundance for all habitats except the oak woodland which was dominated by woodland specialist.
Management changes conducted in 1994 resulted in considerable avian changes in the studied habitats. The removal of woody vegetation from the grassland habitat resulted in the elimination or reduction of many species more associated with shrub communities. Lark Sparrows responded favorably to defragmentation of the grassland and appeared as a breeding species. Success at nesting has remained more elusive. Clearing within the shrub habitat also reduced the appearance of species more associated with woodlands and heavy shrub habitats.
The Golden-winged Warbler is another species of special interest for the Oak Openings. Recognized by Louis Campbell as the species most indicative of the region, the Golden-winged Warbler has disappeared because of habitat changes and pressure from the closely-related Blue-winged Warbler. Banding operations have identified potential habitat at the Ostrich Lane site for the Golden-winged Warbler. Capture and sightings have been associated with the shrub habitat in relationship to oak woodland and wet meadow presence.
Monitoring Avian Productivity