| In birds such as House Wrens (Troglodytes aedon), in which males occupy and defend all-purpose breeding territories, females are predicted to select mates based on traits that indicate male quality or territory quality, or both. In house wrens, as in many migratory songbirds, measures of male and territory quality are correlated; the earliest-arriving males are older and larger than later-arriving males, and early-arriving males establish breeding territories in preferred vegetation. The earliest-arriving males are also the first to acquire a mate, as male arrival date and female settlement date are positively correlated. Although this correlation suggests that females prefer traits of early-arriving males, covariation between measures of male and territory quality make it difficult to determine the traits used by females to select mates. Therefore, I designed a series of experiments that disrupted the relationship between male and territory quality to test the hypotheses that female house wrens select mates on two measures of territory quality (territory vegetation and the number of nest cavities on the territory) and three potential measures of male quality (male body condition, song rate, and the use of spider egg sacs by males during nest construction). The results of these studies demonstrate that females do not prefer males that occupy breeding territories in areas of preferred vegetation or contain multiple nest cavities. Females also do not prefer males that are in the best condition, sing at the highest rate, or use arthropod egg sacs during nest construction. Female house wrens may select mates on traits that were either unmeasured or unmanipulated (e.g., male song repertoire size, nest cavity quality). However, I propose that females are not very choosy when selecting a mate and maximize their reproductive success by mating quickly because the costs of mate searching and delayed breeding outweigh the benefits of being selective. |
