Response of avian and arthropod communities to native grass restoration in central Georgia, USA
McMellen, Angela Barbara
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North American grassland birds are declining more rapidly than any other group of birds. Reasons for decline include habitat fragmentation, alteration, and destruction. The southeastern United States provides both breeding and winter habitat for grassland birds. I investigated responses of bird communities during breeding and winter seasons, and summer arthropod communities to current land management practices (annual mowing and periodic burning), and experimental native grass restoration. Study plots encompassed the spectrum of available habitat, from open agricultural fields to pine stands with low basal area and grassy understory. Native warm season grasses were established successfully in an open, agricultural landscape and 1.2-4 ha forest openings. Restored plots had tall, distinct bunches of native grass and little shrub cover. No differences were detected between breeding bird communities of restored and control plots. Winter bird abundance was highly variable between years, but consistently greater in restored plots. Native warm season grass plots supported substantial numbers of shrub-scrub and forest-disturbance birds during breeding seasons, and grass-herb and shrub-scrub birds during winters. Shrub-scrub birds were negatively correlated with forest cover in a 1-km buffer around plots during breeding and winter seasons. Grass-herb birds were positively correlated with grass cover during breeding and winter seasons. No relationship was detected between grass-herb birds and forest cover during breeding seasons; a negative relationship was detected during winter. Open woodlands had the highest total conservation value during summer and winter, but differences were not significant, suggesting all plots contributed conservation value to the system. Managing for native grass and forb cover may increase arthropod abundance. Arthropod abundance and family richness were greatest in plots with little canopy cover and much grass and forb cover. Contrary to expectations, fire ants (Solenopsis invicta) did not negatively impact arthropod abundance or richness. Orthopteran abundance was lowest in mowed treatments. Araneae were abundant in all but the densest forest treatment. One management prescription will not maintain a diverse community of early successional birds in the Southeast. A mixture of grassland types, including native grasslands, is desirable across the landscape.