How and why do the mating opportunities of males and females differ in natural population of animals? Previously we showed that females have higher mating opportunities than males in the Kentish plover Charadrius alexandrinus. Both parents incubate the eggs, and males provide more brood care...

The study of primary sex ratio adjustment in birds is notorious for inconsistency of results among studies. To develop our understanding of avian sex ratio variation, experiments that test a priori predictions and the replication of previous studies are essential. We tested if female blue tits...