The differential functions of distinct morphological traits as sexual signals among closely related populations are associated with a potential role of sexual selection in population divergence and speciation. The cosmopolitan barn swallow Hirundo rustica complex consists of 6 subspecies, which...

Female birds that engage in extrapair mating may choose extrapair mates that are genetically compatible, increasing their fitness through genetic benefits, such as increased heterozygosity, to their offspring; or choose mates that are heterozygous at one or more loci. Here, we describe the...

Nestling begging behavior is usually characterized by a behavioral response of increasing begging levels with an increase in nestling need or hunger. Recent evidence for the possible effect of learning on begging intensity raises the question of how learning can shape this response rule. In...

Studies of cooperative breeding have largely ignored the role of conflict among helpers and how it shapes group dynamics and helping behavior. In the present study, performing laboratory experiments with cooperatively breeding cichlids from Lake Tanganyika, we show that secondary group members...