Evaluation of the effects of methoprene and BTI (Bacillus thurinqiensis israelensis) on non-target organisms: A summary of Red-winged Blackbird (Aqelaius phoeniceusl and bird community studies before-and-after one year of treatment

Abstract

The overall objective of the bird studies is to determine if treatment of wetlands with methoprene and/or BTI directly or indirectly affect bird growth, reproduction, behavior, or populations. The Red-winged Blackbird (Aqelaius phoeniceus) was chosen for this study for several reasons. First, Red-winged Blackbirds depend on an aquatic-based food supply during the breeding season (Orians 1961, 1980) and applications of insecticides may have food-chain effects by altering aquatic insect populations. Second, Red-winged Blackbirds nest in high densities within many wetlands, allowing collection of enough samples for reasonable power in statistical analyses. Finally, results from this species may be related to possible effects on other altricial songbirds with similar life histories. Many of these species are not present in large enough numbers or are difficult to study because of secretive habits and hence, adequate samples are difficult to obtain (see Conservation Foundation 1989). In this report we summarize work completed on before- and-after (B-A) study sites in 1988, 1989, and 1990 (pre-treatment) and make comparisons with data collected in 1991 (treatment).