Effects of DDT treatments applied for tsetse fly control on white‐browed sparrow‐weaver (Plocepasser mahali) populations in NW Zimbabwe

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Abstract
Summary: Colony density and size, and numbers of white‐browed sparrow‐weavers were investigated in Colophospermum mopane‐Julbernardia globiflora woodland treated from nought to five times with DDT for tsetse fly control. Colonies were absent from Julbernardia woodland. Estimated densities in sprayed and unsprayed mopane woodland were 74 and 71 colonies per km‐2, respectively. Colony size varied with area and time but not with spray treatment. In 1987, colonies at the spraved northern end of the study area were twice the size of those in the unsprayed, drought‐affected south. Two years later, after good rains, colony size in sprayed and unsprayed areas was similar.Residues of DDT, DDD and DDE were measured in birds collected from sprayed and unsprayed areas 3,5,9,12,15 and 17 months after treatment. Residue levels in birds from the sprayed area fell from 3 months after treatment to reach background levels at 12 months. No adverse effects were noted. The most heavily contaminated bird contained 1083 μg DDT‐equivalents g‐1carcass lipid, less than half the maximum amount found in white‐headed black chats Thamnolaea arnoti and red‐billed wood‐hoopoes Phoeniculus purpureus, whose populations collapsed after spraying. Dietary differences probably account for differing exposure and population responses to tsetse spraying operations.Résumé: On a étudié la taille et la densité des colonies ainsi que le nombre de moineauxtisserins à sourcil blanc dans des forêts de Colophospermum mopane‐Julbernardia globiflora traitée de zéro à cinq fois par an au DDT pour lutter contre la mouche tsé‐tsé. Il n'y avait pas de colonies dans la forêt de Julbernardia. Les densités dans la forêt de mopane traitée et non traitée étaient estimées respectivement à 74 et 71 colonies par kilomètre carré. La taille de la colonie variait selon l'endroit et le temps mais pas en fonction du traitement par aspersion. Au début, la taille des colonies de l'extrémité nord, traitée, était le double de celle de l'extrémité sud, non traitée et touchée par la sécheresse. Deux ans plus tard, après de bonnes pluies, la taille des colonies était identique aux deux endroits, traités et non traités.