Nest building, sexual selection and parental investment

Abstract

Avian nest building has traditionally been viewed as resulting in natural selection advantages, but it is also been associated with courtship and pair formation. We hypothesize that nest-building activity could be used as a sexually selected display, allowing each sex to obtain reliable information on the condition of the other. In this paper, we test the`good parent' process in a scenario where nest size is a sexually selected trait. Thus, individuals with more extreme displays (larger nests) might obtain bene®ts in terms of either parental investment or dierential parental investment by the partner. We predicted that: (1) species in which both sexes contribute to nest building have larger nests than those in which the nest is built only by one sex, because both sexes are using the nest-building process as a signal of their quality; (2) species in which both sexes work together in the nest-building process invest more in reproduction, because each can assess the other more reliably than in species where only one sex participates in nest building; and (3) in light of the two preceding predictions, nest size should be positively related to investment in parental care. A comparative analysis of 76 passerine species con®rmed that nest size, relative to the species' body size, is larger when both sexes build the nest and that species with a larger nest relative to their body size invest more in reproduction.

Smaller Eastern Olivaceous WarblerHippolais pallida elaeicaNests Suffer Less Predation than Larger Ones

“…This finding is contrary to the prediction of "sexual display" hypothesis (Palomino et al 1998, Soler et al 1998b) that nest size should be positively related with fledging success because only individuals in good condition are supposed to build large nests, as nest building is costly in terms of energy expenditure and predation risk (Zahavi 1987, Soler et al 1998b). Thus, individuals building large nests should also be better parents and nest size may be considered as an indicator of the readiness of the builder(s) to invest in reproduction (Soler et al 1998b). In the Olivaceous Warbler, however, nests may signal phenotypic quality of the builder through different characteristics.…”

“…where: a -smallest radius, b -largest radius, z -fraction of an ellipsoid = ½ for cup-shaped nests (Soler et al 1998b).…”

“…As both sexes participate in nest building (see Methods), nest-size variation may have a sexual selection component (Soler et al 1998a(Soler et al , 1998b. Fledging success (the most important fitness correlate) was negatively related to nest volume, and this relationship persisted even when only nests that produced at least one fledgling were considered.…”

“…Avian nests are special constructions in which eggs and young develop (Soler et al 1998b). Nest building has been viewed as a result of natural selection, and the nest has been considered an evolutionary compromise between benefits such as protection from adverse environmental conditions during incubation and early nestling stage, reduction in the energetic cost of incubation (Walsberg & King 1978, Sciurine & Kern 1980, Kern 1984, and costs such as energy expended in nest-building and predation risk (Slagsvold 1984, 1989, Lima 1987.…”

“…Nest building has been viewed as a result of natural selection, and the nest has been considered an evolutionary compromise between benefits such as protection from adverse environmental conditions during incubation and early nestling stage, reduction in the energetic cost of incubation (Walsberg & King 1978, Sciurine & Kern 1980, Kern 1984, and costs such as energy expended in nest-building and predation risk (Slagsvold 1984, 1989, Lima 1987. Recently researchers have focused on nestbuilding and nest-size as sexually selected traits (Palomino et al 1998, Soler et al 1998a, 1998b, Soler et al 2001, Fargallo et al 2004.…”