Avian and Aquatic Invertebrate Abundance on Three Agricultural Management Systems in Eastern South Dakota

Due to increased soil erosion, and the cost of fertilizers and energy, many farmers have switched from conventional farming practices to some type of conservation or sustainable farming practice, such as no-till or organic farming. The purpose of this study was to evaluate the impacts of different agricultural management systems on wildlife by determining avian and aquatic invertebrate abundance on a conventional (CON), organic (ORG), and transitional no-till (TNT) farming system. Waterfowl pair abundance varied for individual species on all wetland classes in 1993 and 1994. Total waterfowl pair abundance was generally higher in temporary wetlands on the ORG and/or TNT farming systems, however it was higher in seasonal and semipermanent wetlands on the CON farming system. Species richness was typically higher on the ORG system for individual wetland classes and when all wetland classes were combined. Thirty-six waterfowl broods were counted on the 3 farming systems between both sampling years, however only 5 of these were observed on the CON farming system. Abund ance of non-waterfowl breeding birds, both individual species and total birds, in agricultural fields and wetlands was typically higher on the ORG and/or TNT farming systems. Results indicated that abundance for 11 species was significantly different (E \u3c 0. 05) in agricultural fields. Dickcissels (Spiza americana) and western meadowlarks (Sturnella neglecta) in 1993 oats and yellow-headed blackbirds (Xanthocephalus xanthocephalus) in 1993 alfalfa were found to be significantly more abundant on the CON system. The remaining B species were significantly higher on the ORG and/or TNT farming systems. Ten avian species were found to have significant differences in abundance in wetlands. Common yellowthroat (Geothlypis trichas) abundance was significantly higher (P \u3c 0.05) in seasonal wetlands and yellow-headed blackbirds in semipermanent wetlands on the CON farming system in 1994. Abundances of the other B species were significantly higher on the ORG and/or TNT farming systems. Species richness of non-waterfowl breeding birds in agricultural fields and wetlands was typically higher on the ORG and/or TNT farming systems. No distinct trends in aquatic invertebrate abundance were found. However, generally, invertebrate abundance was slightly higher in seasonal wetlands on the chemical-free (ORG) farming system, but was higher in semipermanent wetlands on the chemical (TNT) farming system. Total invertebrate abundance had similar fluctuations throughout both sampling y ears in both wetland classes. Some taxa significantly (E \u3c 0. 10) decreased in abundance after herbicide applications, however abundance for other taxa increased. In 1993, taxa richness was significantly higher (P \u3c 0. 05) in seasonal wetlands on the ORG system, but was significantly higher in semipermanent wetlands on the TNT farming system. No differences in taxa richness were found in 1994. Overall, avian abundance and richness was typically higher on the ORG and/or TNT farming systems and was probably associated with residual cover on the TNT system and with crop rotations, smaller fields, numerous cover types, and the lack of chemicals on the ORG system. Most comparisons of aquatic invertebrate abundance and richness between the chemical-free (ORG) farming system and the chemical (TNT) farming system were inconclusive