Occurrence and consequences of DDT residues in woodland birds following tsetse fly spraying operations in NW Zimbabwe.
Abstract
Concentrations of DDT and its metabolites were compared over space, time, feeding strategy and diet in the striped kingfisher (Halcyon chelicuti), red-billed wood-hoopoe (Phoeniculus purpureus) and 5 songbird species - white-headed black chat (Thamnolaea arnoti [Myrmecocichla arnoti]), black tit (Parus niger), chinspot flycatcher (Batis molitor), white helmet shrike (Prionops plumatus) and white-browed sparrow-weaver (Plocepasser mahali). The sparrow-weaver fed mainly on seeds, but the remaining species were insectivorous. The kingfisher, chat and helmet shrike fed heavily on secondary consumers. DDT residue concentrations 1-3 months after treatment reflected feeding site more than diet. Geometric means varied between species by up to 15 times. Highest concentrations were found in the wood-hoopoe and chat, which sometimes foraged on sprayed tree trunks, while lowest concentrations were found in the flycatcher and helmet shrike, which foraged mainly in tree and shrub canopy. Depending on species, geometric mean concentrations of DDT equivalents fell from 90-1300 µg g-1 lipid weight at 1-3 months post treatment to 16-87 µg g-1 lipid weight at 14-17 months. The proportion of DDE in ΕDDT increased from 23-77% to 69-98% over the same period. Interspecific variation at 14-17 months still reflected feeding site rather than trophic accumulation. Populations of the wood-hoopoe and chat declined over 2-3 years in sprayed areas by about 90%, but no differences attributable to spraying were detected in the other species.