▪ Abstract It has recently been argued that the paradox of helping behavior in birds has been
solved. This optimism may be premature. I argue that there is no obvious dichotomy …

▪ Abstract Extra-pair paternity (EPP) is extremely variable among species of birds, both in its
frequency and in the behavioral events that produce it. A flood of field studies and …

Despite great interest in the use of extra–pair mating as a tool for examining female choice
and intersexual selection, the underlying assumption of female control has proved difficult to …

Monogamous and polygynous male songbirds generally differ in their breeding season
profiles of circulating testosterone. Testosterone level spikes early in the breeding season of …

In many species of monogamous birds females copulate with males other than their social
mates, resulting in extrapair fertilizations. Little is known about how females choose …

In the three decades, since Birkhead and Møller published Sperm competition in birds
(1992, Academic Press) more than 1000 papers have been published on this topic, about …

Many socially monogamous species paradoxically show signs of strong sexual selection,
suggesting cryptic sources of sexual competition among males. Darwin argued that sexual …

Recent models of the evolution and dynamics of family structure in cooperatively breeding
vertebrates predict that the opening of breeding vacancies in cooperatively breeding groups …

Sperm morphology evolves rapidly, resulting in an exceptional diversity of sperm size and
shape across animal phyla. This swift evolution has been thought to prevent fertilizations …

The red‐backed fairy‐wren is a socially monogamous passerine bird which exhibits two
distinct types of breeding male, bright males that breed in bright red and black plumage and …