Social mating system and reproductive success in house wrens

Current models explaining the establishment and maintenanceof social monogamy and polygyny within avian populations typicallyassume that the reproductive success of polygynous males exceedsthat of monogamous males. This assumption is almost always supportedwhen the number of fledglings or recruits to future breedingpopulations is used to measure adult reproductive success. However,recent studies using DNA markers indicate that simple countsof fledglings or recruits may be a poor estimator of the numberof nestlings sired by the social father. In this paper, we comparethe number of genetic offspring produced by socially monogamousand polygynous house wren (TrogiodyUs atdon) males in nestsat which they were the social father. Polygynous males did,in fact, sire more nestlings in their own nests than did monogamousmales. Moreover, although we have not identified the sires ofextrapair nestlings, we document that even when all extrapairnestlings in this population are hypotheticaOy assigned to monogamousmales, die total reproductive success of polygynous males exceedsthat of monogamous males. These results and those of severalother recent studies are consistent with the assumption thatpolygynous males produce more offspring than monogamous males.