PARENT SESSION
Oral Session #59: Conservation Ecology: Terrestrial Biodiversity. Presiding: K. Schulz.
Thursday, August 9, 2001. 8:00 AM to 12:15 PM. Madison Ballroom D.
A Regional analysis of the effects of grassland fragmentation on nesting success of breeding birds.
HERKERT, JAMES1, REINKING, DAN2, WIEDENFELD, DAVID2, WINTER, M3, ZIMMERMAN, JOHN4, JENSEN, WILLIAM5, FINCK, ELMER5, KOFORD, ROLF6, WOLFE, D.2, SHERROD, S.2, JENKINS, M.2, FAABORG, J.3, ROBINSON, S.7, 1 2 3 4 5 6 7
ABSTRACT- Prairies once were the largest vegetative province in North America. However, loss of prairie has exceeded that of most other major ecosystems on the continent such that only 4% of an estimated 68 million ha of North American tallgrass prairie remains today. One major consequence of this extensive habitat loss has been a significant increase in the degree of fragmentation of remaining grassland habitats. Grassland fragmentation has been shown to significantly reduce both the occurrence and density of breeding birds in small fragments, but there are relatively few data on the extent to which grassland bird nest predation and nest parasitism rates are correlated with grassland area. We tested the hypothesis that nest predation and brood parasitism rates of four species of grassland birds were related to prairie fragment area within five states in the mid-continental United States. During our study we monitored the fates of nearly 3,000 nests in 39 prairie fragments ranging from 24 to >40,000 ha in size. We found that throughout the mid-continental United States, nest predation rates were significantly higher in small prairie fragments. Brood parasitism rates, however, were not consistently related to prairie area and appeared to be more strongly associated with regional cowbird abundance than prairie area. Differences in nest predation rates between large and small fragments suggest that fragmentation of grassland habitats, especially native prairies, may be contributing to regional declines of grassland birds. Therefore, maintaining grassland bird populations may require protection and restoration of large prairie areas.
KEY WORDS: Fragmentation, Prairie, Birds