Avian Nest Success And Snake Occurrence In Restored And Remnant Prairie Complexes In Northwestern Iowa
L. Embere Hall, Iowa State University, Natural Resource Ecology and Management, 124 Science II, Ames IA 50011; (515) 294-9716; FAX (515) 294-5468; embere@iastate.edu
Rolf R. Koford, Iowa State University, Natural Resource Ecology and Management, 124 Science II, Ames IA 50011
We examined the effect of grassland restoration on the reproductive success of prairie nesting songbirds in northwestern Iowa. In Iowa, less than 0.1% of the original tallgrass prairie ecosystem remains. Government agencies have responded to this loss with land acquisition and grassland restoration programs. We compared avian nest success estimates from restored grassland sites to estimates from remnant prairie sites to determine the impact of restoration efforts on local bird productivity. Smooth brome (Bromus inermis) and sweet clover (Melilotus spp.) compose the dominant vegetative cover on restored sites. Plant communities on remnant study areas include a substantial forb component that is not available on the restored sites. During the 2003 and 2004 breeding seasons we located and monitored nests on 12 restored and 7 remnant tracts of grassland in northwestern Iowa. Dickcissels (Spiza Americana), bobolinks (Dolichonyx oryzivourorus), red-winged blackbirds (Agelaius phoeniceus) and clay-colored sparrows (Spizella pallida) nested in both restored and in remnant sites. Preliminary data analysis indicates that nest survival rates are significantly higher on remnant prairie sites. During the 2004 season we also evaluated relative snake abundance on both landscapes. Through the use of 130 artificial shelters placed in the interior of restored and remnant study areas we captured individuals of 4 snake species. Two of these species, common garter snakes (Thamnophis sirtalis) and plains garter snakes (Thamnophis radix), depredate grassland songbird nests. Relative snake abundance may explain part of the variation in nest success on restored and remnant prairie sites. Results from this study will help managers effectively restore landscapes crucial to declining grassland songbird populations.