The field experiments proposed should allow us to exploit to the utmost the potential for controlled experimentation in a naturalistic field setting. These experiments, combined with naturalistic field observation should allow us to understand molecular processes in terms of their functional importance in the full natural behavioral context. We will arrive at an understanding of the importance of habituation in maintaining the territorial system of the white-crowned sparrow, and will understand the possible role of dialects in producing assortative mating and in maintaining the integrity of the breeding population. We will also obtain substantial information regarding the relationship between ecological factors and reproductive success.