This study investigates the fitness benefits of extra-pair fertilizations to both females and males in a marked population of singly-paired-bonded, territorial, dispersed nesting birds with biparental care of offspring. Predictions that females gain material and genetic benefits from the males with whom they mate surreptitiously and that males are more likely to pursue extra-pair fertilizations when they are least likely to reduce fitness with their pair-bonded females. This study will combine field observations of behavior, song analysis, and estimation of reproductive success from biochemically assessed parentage using short tandem repeats in DNA base pairs to identifying highly polymorphic Mendelian loci. The study brings a highly original blending of population analysis and molecular biological assessment of relatedness on issues of general importance in addressing practical problems of species survival of wild birds.
