Traits related to fitness are often pleiotropically linked or otherwise constrained in their expression. Organisms therefore trade between fitness components such as number and viability of their offspring. The physiological mechanisms mediating such trade-offs, however, have been poorly...

Mothers can influence the phenotype of their offspring by adjusting the quality of their eggs in relation to sex and reproductive value of the progeny. Maternal androgens in the eggs of vertebrates may mediate such adaptive early maternal effects. However, the evolution of early maternal effects...

Timing of optimal reproduction can be affected by the presence of multiple broods, with multi-brooded species breeding earlier (and later) than the optimal timing of breeding as compared with single-brooded species that only need to optimize the timing of a single brood. Approximately two-thirds...

Sexually selected infanticide, whereby unmated males obtain a mate by killing the dependent offspring of an already mated female, is a common alternative reproductive strategy in many animals. I estimated the frequency of infanticide in a population of barn swallows, Hirundo rustica, during the...

Among bird species in which males contribute to nest building, sexual selection has favored larger nests. I investigated determinants of nest size in the barn swallow Hirundo rustica and how nest size changed during the period 1977--2003, when tail length (a male secondary sexual character)...