Social mating system, male parental care contribution and life history traits of a southern Sedge Wren (Cistothorus platensis platensis) population: a comparison with northern Sedge Wrens (Cistothorus platensis stellaris)

Abstract

The study of geographic variation of social mating systems can shed new light on our understanding of how ecological variables shape extant mating associations.We report data on the social mating system, parental care and life history traits of a temperate population of southern Sedge Wrens (Cistothorus platensis platensis) in South America. We compared our results with published records of two temperate populations of northern Sedge Wren (Cistothorus platensis stellaris) in North America. The southern temperate population had a lower social polygyny rate, greater male contribution to feeding nestlings and smaller clutch sizes than northern temperate populations. A similar pattern of low rates of social polygyny and smaller clutch sizes in the south versus moderate rates of social polygyny and bigger clutch sizes in the north has been reported for the House Wren (Troglodytes aedon). This suggests that different selective forces may be operating in northern and southern wren populations. Future work in additional study populations is essential to establishing the generality of our results.