Individual variation in life-history trade-offs can be caused by differences in quality and age. We tested for individual variation in parental investment in incubating tree swallows (Tacyhcineta bicolor) subjected to a feather-clipping manipulation. Individual quality influenced how females...

Body condition can affect coloration of traits used in sexual selection and parent--offspring communication by inducing rapid internal changes in pigment concentration or aggregation, thickness of collagen arrays, or blood flux. The recent "makeup hypothesis" proposes an alternative...

Sexual adornments often vary markedly across a species' range, which presumably is owing to differences in local environmental conditions and the associated selection pressures, such as natural versus sexual selection or the relative signaling value of different ornamental traits. However, there...

Many animals develop bold patches of black or brown coloration that are derived from melanin pigments and serve as sexual or social signals. At present, there is much debate among behavioral ecologists over whether melanin-based color signals are costly to produce. Studies that have manipulated...