A combination of laboratory and field investigations of birds has shown that expression of
behavior such as territorial aggression can occur throughout the year in many species and …

Males of many species must allocate limited energy budgets between mating and parenting
effort. The Challenge Hypothesis provides a framework for understanding these life-history …

When selection on males and females differs, the sexes may diverge in phenotype.
Hormones serve as a proximate regulator of sex differences by mediating sex-biased trait …

Sexually selected signals of individual dominance have profound effects on access to
resources, mate choice and gene flow. However, why such signals should honestly reflect …

Male birds frequently face a trade-off between acquiring mates and caring for offspring.
Hormone manipulation studies indicate that testosterone often mediates this trade-off …

Abstract Models of biparental care predict that parents should compensate incompletely for
any change in their partner's investment. Experimental tests have, however, yielded results …

Despite the well-documented benefits afforded the children of invested fathers in modern
Western societies, some fathers choose not to invest in their children. Why do some men …

For male vertebrates, androgens are considered physiological mediators of the trade-off
between mating and parenting effort. About 30 years ago, the challenge hypothesis …

Game theoretical models of biparental care predict that a change in work rate by one parent
should be met by incomplete compensation by its partner. However, in empirical studies on …

One of the common assumptions in the study of the evolution of parental care is that trade‐
offs exist between parental investment and other fitness‐related traits. In general, this body …