Grass Wren

The grass wren (Cistothorus platensis) is a species of passerine bird in the family Troglodytidae. It is widely distributed in central and southern America. The species was described in 1790 by the English ornithologist John Latham and given the binomial name Sylvia platensis. The type locality is Buenos Aires, Argentina. The current genus Cistothorus was introduced by the German ornithologist Jean Cabanis in 1850. The grass wren and the sedge wren were formerly treated as conspecific. They were split based on the results of a molecular phylogenetic study published in 2014. There are 17 recognised subspecies of the grass wren. Grass wrens build two types of non‐breeding nest structures: platforms and dummy nests. Platforms are rudimentary accumulations of grasses concealed between vegetation. Dummy and breeding nests are dome‐shaped with a similar structural layer. The function of these non-breeding nests is unclear, but an experimental study suggests that building non‐breeding nests may be an attempt by males to manipulate the decision of females to breed with a mate they might otherwise reject or to start reproduction earlier than optimal for the females.