The immunocompetence handicap hypothesis was formulated 12 years ago in an attempt to
offer a proximate mechanism by which female choice of males could be explained by …

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 …

In this paper we show how animal personality could explain some of the large inter‐
individual variation in resting metabolic rate (MR) and explore methodological and …

Secondary sexual traits (SST) are usually thought to have evolved as honest signals of
individual quality during mate choice. Honesty of SST is guaranteed by the cost of …

Glucocorticoid (GC) variation has long been thought to reflect variation in organismal
'stress,'but associations between GCs and Darwinian fitness components are diverse in …

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 …

Animals need to adjust reproductive decisions to environmental seasonality. In contrast to
species from the well-studied temperate zones, little is known for tropical birds about the …

Twice a year, normally diurnal songbirds engage in long-distance nocturnal migrations
between their wintering and breeding grounds. If and how songbirds sleep during these …

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

Understanding the mechanisms that link ornamental displays and individual condition is key
to understanding the evolution and function of ornaments. Immune function is an aspect of …