Pesticide risk mitigation of avian wildlife in Iowa agroecosystems
Sauls, Benjamin Tillman
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Modem agricultural practices have had a significant impact on the structure and suitability of agricultural landscapes as habitat for both plant and animal species. Many species of farmland wildlife have demonstrated population declines, which parallel increased herbicide use and altered land management. Habitat loss may often be greater threat to wildlife than pesticide use in agricultural landscapes. Mitigation may not focus on a particular pesticide product but more on the effect of an agricultural practice. The objective of this research project was to quantify the response of avian species to habitat enhancement and to provide forms of compensatory mitigation for pesticide effects on wildlife. During the first phase of habitat enhancement, unsprayed field borders were established along hedgerows on 4 sites and 4 other sites were conventionally farmed and used as reference sites. Northern bobwhite (Colinus virginianus) survival and nesting success were monitored and compared between unsprayed and reference sites. Results indicated that less than 20% of bird locations were on or adjacent to hedgerows on either reference or unsprayed sites. Bobwhite dispersed from hedgerows on reference and unsprayed sites before the borders were established. The next phase of this habitat enhancement research project involved planting a 10 m grass/forb border adjacent to the hedgerow on 3 sites. Three similar sites were conventionally farmed and referred to as reference sites. Bobwhite health indices and the nutritional value of crop contents for bobwhite and ring-necked pheasant(Phasianus colchicus) were measured on all sites. Results indicated that grassy field borders were not effective in increasing body condition indices of northern bobwhite and crop content results were heavily biased by specimens that contained soybean contents. During the spring, grassy border and reference sites were monitored for songbird activity. Avian abundance, species richness and nesting success of songbird species were compared between grassy border and reference sites. Overall, songbird populations were positively correlated with the increased grass/forb composition of the grassy borders. However, the extent of important differences in songbird populations was difficult to determine due to small sample size and limited seasonal data.