Exposure of California quail to organophosphorus insecticides in apple orchards in the Okanagan Valley, British Columbia

We studied the exposure and effect of the organophosphate insecticides azin phos-methyl and diazinon on adult California quail (Callipepla californica) in an apple orchard in the Okanagan Valley, British Columbia. Cholinestera se activity was measured in plasma samples (n = 65) collected from 54 indiv iduals either prior to spraying, immediately (<24 hours) or 10 days after t hree spray events. Mean plasma cholinesterase levels declined significantly (P < 0.05, n = 12) to 61% of pre-spray mean activity (controls) immediatel y following the first spray event, but by ten days had recovered to 86% of mean control activity. Subsequent spray events caused no significant declin es in mean plasma cholinesterase activity. Four of the 26 quail sampled wit hin 24 h of a spray event exhibited plasma-ChE inhibition exceeding 50% inh ibition. Radio-tagged quail (n = 25) were monitored throughout the breeding season to determine use of orchards and detect changes in use patterns res ulting from the spraying of insecticides. Use of orchards by quail varied o ver the summer, with the highest use occurring in May, declining to very lo w use by July. Quail exhibited a diurnal pattern, roosting in sparsely fore sted uplands at night, travelling to orchard areas to feed early each morni ng and returning to roosts at dusk. Orchard use by quail differed during sp ray events compared to non-spray times. During the three hour period immedi ately after spraying (0530-0800), 14-20% of observed quail were in the orch ard, after which use declined to <4%, and returned to 12% by the next day. During non-spray times, 3-13% of radio-tagged the quail were observed in or chard habitat, with the heaviest use (13%) occurring later in the day (0830 -1700 h). Seven radio-tagged quail were predated during the study period. H owever, no deaths could be attributed to insecticide poisoning as carcasses were not in suitable condition for testing. It was concluded that adult qu ail using orchard habitat early in the summer may be acutely poisoned by an ti-cholinesterase insecticides, but the risk of exposure declined over the summer.