Falkland Island Sedge Wrens (Cistothorus Platensis) Imitate Rather Than Improvise Large Song Repertoires

Among songbirds, does reduced fidelity to a breeding site lead to vocal improvisation? Data for Cistothorus wrens suggest it does, because North American Sedge Wrens (C. platensis) have low breeding-site fidelity and improvise their large song repertoires, but sedentary or site-faithful populations of this and other Cistothorus species in the Neotropics and North America all imitate. We attempted to falsify this hypothesis by studying extreme south-temperate zone populations of Sedge Wrens in the Falkland Islands. We banded and recorded males on Kidney Island and Carcass Island, and then compared song matching among males both within and between islands. Birds on those islands were highly site-faithful from one breeding season to the next. Song repertoires were large, up to 400 in one bird, and songs of birds within an island were more similar to each other than to songs on the other island, showing that these birds do imitate. These results further support the idea that site fidelity promotes imitation of neighbors, and continue to highlight the unique correlation between reduced site-fidelity and song improvisation in the North American Sedge Wren.