Cases where less ornamented males are favored through sexual selection are rare among birds. Here we show, based on data from 3 consecutive breeding seasons, that male blue tits with less ultraviolet (UV)-ornamented crown feathers sire more offspring. This pattern was mainly driven by the higher...

Plumage coloration is generally perceived as a static trait and therefore not a good indicator of current condition. However, changing of feather colors after molt does occur and may have important implications for signal function and sexual selection. We studied longitudinal changes in blue tit...

Migratory birds have to invest much energy into flight to reach their summer and winter quarters. Many studies have shown how migration affects body physiology, including the accumulation of energy stores and the reduction of nonessential organs. In spring, the costs of migration may trade-off...

Females of many species copulate more frequently than necessary to fertilize their eggs despite the potential costs. Several studies, particularly on socially monogamous birds, have suggested that females obtain immediate material benefits by trading copulations for nutrients or other resources....

In birds, a high degree of paternal care is expected to correlate with a relatively low frequency of extrapair paternity. If females seek extrapair copulations, they may lose fitness because their partners may reduce paternal care. Conversely, a high degree of paternal care might give females...

The type of social and genetic mating system observed in birds is influenced by the need of both sexes to provide parental care. In woodpeckers, unlike most birds, females are partially emancipated as males provide most of the care including nocturnal incubation. We analyzed the mating system of...

Intraspecific sexual and social communications are among the most important factors shaping costly color traits in birds. Condition capture models assume that only animals in superior condition can develop and maintain a colorful plumage. Although there is good evidence that carotenoid-based...

Consistent between-individual differences in context-general behavioral traits (often called personality traits) are particularly interesting for behavioral ecologists because they might show unexpected cross-context correlations and explain maladaptive behavior. In order to understand their...

Most socially monogamous bird species engage in extra-pair mating, and consequently males may adopt various behavioral strategies to guard paternity. However, the relationship between mate guarding and extra-pair paternity is unclear: low levels of extra-pair paternity can be associated either...