Sexual dimorphism and parental care in the wren-like rushbird Phleocryptes Melanops

Abstract

The Furnariidae is a very diverse family of Neotropical passerines in which the role ofsexes in nest attendance and the possible existence of sexual dimorphism still remain poorly known for most species. Here, in a study spanning two breeding seasons, we analyzed the sexual dimorphism in morphology and the parental roles during incubation and chick rearing in the Wren-like Rushbird Phleocryptes melanops, a typical furnariid distributed in the southern wetlands of South America. Given previous knowledge of natural history of this family, we expected a slight dimorphism in size and a similar role of the sexes in parental care. Adults were captured and measured, and blood samples taken for molecular sex determination. Males had on average, 10.3%, 10.2%, 5.3%, and 4.4% larger bill lengths, tail lengths, wing chord lengths, and tarsus lengths than females, respectively, whereas no significant sexual differences were found for bill widths and depths. In addition, we found that both parents participated similarly in all reproductive activities during incubation and nestling stages, in line with the general pattern reported in furnariids. The sexual selection hypothesis may best explain the size differences between the sexes and in the behaviour of the species at the beginning of the nesting cycle.