• Pearce, P.A.
  Canada Wildlife Service
  
• Peakall, D.B.
  Canada Wildlife Service
  
• Erskine, A. J.
  Canada Wildlife Service
  

The impact on breeding birds of a forest spray operation against spruce budworm in New Brunswick in 1975 is assessed by two independent methods intensive survey of singing males along walked transects and extensive surveys along motored transects. Extrapolation of data derived from these studies indicates that several million singing male birds mostly canopy feeders, were killed. Birds feeding on or near the ground were not significantly affected. It seems likely that phosphamidon caused the major portion of the mortality, but that fenitrothion was also involved. The application of aminocarb, in a spray format which included fenitrothion, also resulted in significant mortality to canopy feeders. Inadvertent overdosing, resulting from imprecise positioning of spray aircraft, may have contributed locally to the hazard to birds. Spray regimes were more complex and phosphamidon played a greater role in the 1975 operation than in spray programs conducted in the province in preceding years. For those reasons, songbird mortality in 1975 is judged to have been exceptionally and atypically high.