Plasma cholinesterase characteristics in native Australian birds : significance for monitoring avian species for pesticide exposure

Cholinesterase-inhibiting pesticides are applied throughout Australia to control agricultural pests. Blood plasma cholinesterase (ChE) activity is a sensitive indicator of exposure to organophosphorus insecticides in vertebrates. To aid biomonitoring and provide reference data for wildlife pesticide-risk assessment, plasma acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were characterised in nine species of native bird: King Quails (<i>Excalfactoria chinensis</i>), Budgerigars (<i>Melopsittacus undulatus</i>), White-plumed Honeyeaters (<i>Lichenostomas penicillatus</i>), Yellow-throated Miners (<i>Manorina flavigula</i>), Willie Wagtails (<i>Rhipidura leucophrys</i>), Australian Reed-Warblers (<i>Acrocephalus australis</i>), Brown Songlarks (<i>Cincloramphus cruralis</i>), Double-barred Finches (<i>Taeniopygia bichenovii</i>) and Australasian Pipits (<i>Anthus novaeseelandiae</i>). Plasma ChE activities in all species were within the range of most other avian species and all but one contained AChE and BChE; no AChE was present in King Quail, which has not previously been reported for any species. The lowest detectable plasma AChE activity was 0.10 μmol min^–1 mL^–1 in Budgerigars and the highest was 0.86 μmol min^–1 mL^–1 in Australian Reed-Warblers. BChE in the plasma ranged from 0.37 μmol min^–1 mL^–1 in Double-barred Finches to 0.90 μmol min^–1 mL^–1 in White-plumed Honeyeaters and Australian Reed-Warblers. The lowest proportion of AChE was found in Budgerigars (12.8%) and highest in Willie Wagtails (67.8%). No differences were detected in ChE activity at any time of day in Budgerigars and Zebra Finches (<i>Taeniopygia guttata</i>), although there was a significant difference in all ChE activity between seasons in Zebra Finches.<br>