Nest size and hatchling sex ratio in chinstrap penguins

Abstract

Variation in the sex ratio at hatching in the chinstrap penguin Pygoscelis antarctica was investigated, using molecular sexing to test predictions of sex allocation theory. The sex ratio was slightly male-biased (0.54) but did not differ significantly from parity. The proportion of males increased with nest size, an estimator of parental quality in chinstrap penguins. Highquality parents were able to produce and rear a higher proportion of male offspring, the more costly sex in this slightly sexually dimorphic species. Our results may be in agreement with Trivers and Willard's (1973) argument on biases in the offspring sex ratio being contingent on parental condition or quality.

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

“…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.…”

Biparental Care of Chinstrap Penguin: Molecular Sexing and Life History in the South Shetland Islands, Antarctica

“…Since both parents are essential to reproductive success, the optimum sex ratio is 1:1 for maximum Chinstrap penguin breeding success, is to be expected. e species actual sex ratio for each breeding colony represents population response to local genetic, environmental, behavioral and evolutionary factors, so it is an important parameter to understanding population life history (Seger & Stubble eld, 2002;Fargallo et al, 2004;Jenouvrier et al, 2010).…”