This paper is based on the discussions and conclusions of a workshop convened in York, England, in January 2004 to consider methods for improving assessments of long-term risks of pesticides to birds and mammals for regulatory purposes in the United Kingdom. By comparing the timing of pesticide applications with the timing of wildlife breeding period, and considering the pesticide effects that could occur during the breeding period, this approach estimates the cumulative reproductive response of individuals in a breeding population based on the decision framework developed, and derives an overall metric of impact of the pesticide on reproduction.