EFFECTS OF INSECTICIDE USE ON BREEDING BIRDS IN CHRISTMAS TREE PLANTATIONS IN QUEBEC

This research, which was carried out in the spring of 1989 and 1990 in seven balsam fir (Abies balsamea) plantations in southeastern Quebec, examines potential deleterious effects of three insecticides (i.e. di methoate, diazinon and insecticidal soap) on breeding American Robins (Turdus migratorius) (n = 87 nests) and Song Sparrows (Melospizsa melo dia) (n = 41 nests). Through analyses of blood serum cholinesterases ( AChE and BChE) activity both prior to and the second day following app lications of the two organophosphorus insecticides, we showed that adu lt American Robins, Song Sparrows and Chipping Sparrows (Spizella pass erina) breeding in the treated plantations were exposed to diazinon an d dimethoate (p < 0.05). Signs of exposure to diazinon (p < 0.05) were also found in young American Robins. However, despite sharp reduction s in blood ChE (and, in some cases, marked inhibition confirmed by 2-P AM reactivation), no cases of adult mortality were recorded following the treatments. Cases of complete or partial mortality were recorded i n American Robin and Song Sparrow nests, even among control birds (non -exposed birds). No mortality was recorded for broods exposed to the i nsecticidal soap. Abandonment of nests and egg infertility were ruled out as possible causes of mortality. The cases of total mortality obse rved in American Robin and Song Sparrow broods exposed to dimethoate w ere similar to those recorded for control nests (18 and 25% compared t o 14 and 21%, respectively). However, among American Robin and Song Sp arrow nestlings exposed to diazinon, essentially twice as many cases o f total mortality (31 and 38%, respectively) were recorded as for the control nests. It appears that American Robin eggs are sensitive to di azinon and dimethoate, particularly when spraying is carried out early in the incubation stage. In the case of the Song Sparrow, it is mainl y the nestlings that succumb after diazinon is sprayed on them or when dimethoate applications are made during the egg stage.