Sexual selection and reproductive investment in house wrens (Troglodytes aedon)

An individual's fitness depends on both the quality and quantity of offspring it is able to produce over its lifetime. For iteroparous species, the optimal allocation of investment to a particular breeding attempt should be mediated by its reproductive value relative to the costs to and benefits from future reproduction. Reproductive value might be influenced by mate or territory quality, environmental variables such as food abundance, or opportunities to secure additional matings. Within a breeding attempt, individuals can maximize reproductive success by choosing a high quality mate, investing more in offspring with high reproductive values, and taking advantage of additional mating opportunities if the benefits of doing so exceed costs. Individual tradeoffs between investment in current and future reproduction may result in conflicts of interest between parents if, for example, a parent cannot simultaneously provision young and attract mates.; I investigated mate choice and reproductive investment decisions in the house wren (Troglodytes aedon), a facultatively polygynous cavity nester. In contrast to what is observed in a congener (winter wren, T. troglodytes), I found that the presence of empty (or 'cock') nests had no effect on mate choice or maternal investment in reproduction, but the availability of cavities within territories did affect male and female reproductive investment. Females mated to males with surplus nest boxes added to their territories laid larger clutches at early season nests and produced more males per clutch than females mated to males with single cavities in their territories. These results suggest that female house wrens might use cavity availability to assess male quality. Males with surplus nest boxes added to their territories sang more than males with single nest boxes, but this increased song rate had no effect on paternal provisioning efforts. Both males with surplus cavities and males with single cavities in their territories were less likely to provision at early season nests than at late season nests. Costs of provisioning at early season nests might be high for males, regardless of mate attraction opportunity, if males that provision at early season nests are less likely to rear second broods.