The negative co‐variation of life‐history traits such as fecundity and lifespan across species
suggests the existence of ubiquitous trade‐offs. Mechanistically, trade‐offs result from the …

Avian duetting is an unusual but taxonomically widespread phenomenon, occurring in over
400 species, representing 40% of bird families. Duets vary in form from loosely overlap** …

Life history theory seeks to explain the evolution of the major features of life cycles by
analyzing the ecological factors that shape age-specific schedules of growth, reproduction …

Steroid hormones have similar functions across vertebrates, but circulating concentrations
can vary dramatically among species. We examined the hypothesis that variation in titres of …

In vertebrates, stressors such as starvation or predator attacks stimulate the rapid elevation
of circulating glucocorticoid hormones, triggering physiological and behavioral responses …

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 …

Berthold's classic study of domesticated roosters in 1849 demonstrated that testicular
secretions are necessary for the normal expression of aggressive behaviour. Although this …

Androgen levels show strong patterns throughout the year in male vertebrates and play an
important role in the seasonal modulation of the frequency, intensity and persistence of …

Glucocorticoid (GC) hormones are important phenotypic mediators across vertebrates, but
their circulating concentrations can vary markedly. Here we investigate macroevolutionary …

Tropical birds offer unique opportunities to test ecological and evolutionary theory because
their life history traits are so diverse and different from temperate zone models upon which …