We briefly review methods for assessing the impact of forest insecticide spray programs on forest songbirds and discuss the applicabilities of various census techniques. Data obtained on brain acetylcholinesterase enzyme (AChE) levels in live birds collected postspray are reanalyzed. We conclude that these data show a severe collection bias in favor of birds with a low (e.g., approximately below 30% from control) level of AChE inhibition. Possible solutions are discussed. Finally, we suggest that multiyear impact assessment studies involving a number of reproductive parameters are needed to evaluate the effects of nonpersistent insecticides on forest songbirds.