Rapid southward and upward range expansion of a tropical songbird, the Thrush-like Wren (Campylorhynchus turdinus), in South America: a consequence of habitat or climate change?

Abstract

The Thrush-like Wren (Campylorhynchus turdinus) is a polytypic, non-migratory, cooperatively breeding species of bird widely distributed in central South America. In recent decades it has expanded its range by approximately 24%, based on a published map of its distribution in the mid-1980s and recent reports submitted to eBird up through March 2017. The northwestern subspecies, C. t. hypostictus, dramatically expanded its elevation range upward from approximately 1200 m to 4200 m a.s.l. in the Peruvian Andes. During 1977–2015 the southwestern subspecies, C. t. unicolor, dramatically expanded the southern border of its range from central Brazil and northern Paraguay (approximately 22°06'S) southward into northeastern Argentina and throughout Paraguay to 29°40'S in southeastern Brazil, extending its range east-southeast approximately 934 km at a rate of 24.6 km/yr, and latitudinally southward 838 km at a rate of 22.1 km/yr. It also expanded its range westward into the relatively dry Chaco of western Paraguay and north-central Argentina. Midwinter records near the southern border of its range in northeastern Argentina suggest it is non-migratory. Because of its affinity for disturbed habitats, its range expansion has been attributed to deforestation, but its range expansion is also consistent with the prediction that organisms are extending their geographic distribution toward higher latitudes and elevations as a consequence of climate change.