Effects of pesticides on songbird productivity in conjunction with pecan cultivation in southern Georgia: A multiple-exposure experimental design

A prototypic experimental design was used to assess sublethal effects of multiple and varied organophosphates and carbamates on reproduction in birds. The design allowed for classification of pesticide exposure according to toxicity of applied compounds and type and frequency of applications. Daily survival rates (DSRs) of nests, eggs, and nestlings were determined for northern mockingbirds (Mimus polyglottos), brown thrashers (Toxostoma rufum), and northern cardinals (Cardinalis cardinalis) nesting along edges of pecan orchards and row crops in southern Georgia. Egg and nestling DSRs for all species combined varied inversely (P < 0.05) with exposure. Nestling weight gain was reduced (P < 0.05) with increasing exposure levels in northern mockingbirds and brown thrashers. Parenting behavior in northern cardinal and northern mockingbird did not differ (P > 0.05) among three exposure levels. Brain cholinesterase activities were age-dependent and substantiated adult, but not nestling, exposure. Results suggest that increasing exposure to pesticides may reduce songbird productivity.