PS 25-93
Low forest bird migration proportions in sub-Antarctic and temperate forests of southwestern South America

Tuesday, August 12, 2014
Exhibit Hall, Sacramento Convention Center
Rajan Rijal, Sub-Antarctic Biocultural Conservation Program, University of North Texas, Denton, TX
Jaime E. Jiménez, Sub-Antarctic Biocultural Conservation Program, IEB-UMAG-UNT, Chile
Ricardo Rozzi, Sub-Antarctic Biocultural Conservation Program, IEB-UMAG-UNT

The UNESCO Cape Horn Biosphere Reserve (CHBR) at the austral end of the Americas is a landmark for global biodiversity conservation hosting the world’s southernmost forests. These Magellanic sub-Antarctic forests are dominated by a mix of evergreen broadleaf Nothofagus betuloides, deciduous N. pumilio, N. antarctica, and a mosaic of moorland, high-Andean, coastal, and wetland habitats. Birds of the sub-Antarctic forests of South America exhibit features of island settings, such as high endemism, low diversity, genetic isolation, and on-going specialization processes. Compared to North American temperate and boreal forest bird assemblages, South American ones are subjected to a less contrasting weather patterns characterized by moderate winters and mild summers, which we hypothesize that is associated with a lower proportion of migratory birds. Here we report the proportion of migratory birds in South American temperate and sub-Antarctic forests along 25 degrees of latitude, and compared it with the proportions described for North American equivalent latitudinal regions. Using 13 years of standardized monthly mist-netting at Omora Park on Navarino Island (55oS), combined with bird censuses in 61 sites distributed throughout the CHBR, and censuses conducted on Chiloe Island (42oS) and Fray Jorge National Park (30oS), we analyzed the patterns of seasonal migration.  


In the CHBR we captured 22 forest bird species. More than half of the species (63.7%) are residents, 13.6% are partial migrants, and only 22.7% were migrants. Furthermore, only 3 species are longer distance migrants; Elaenia albiceps is the only long-distant migrant, wintering in tropical forests of the Amazon. On Chiloe Island, out of 33 forest bird species, 15.2% are migrants, whereas in Fray Jorge National Park only 11.1% of the 27 forest bird species are migratory. These proportions of migratory species are ca. three times lower than those reported for North America where approximately 30%, 51%, and 70% of the bird species migrate south in autumn at 30oN, 42oN, and 55oN, respectively. Regarding climate, annual temperature range recorded in Alaska at 64ºN for the years 2009-2012 was 47.9ºC, whereas for the same period, the annual temperature range recorded at Omora Park (55oS) was 8.9ºC; i.e.,  annual temperature range is 5 times lower in Magellanic sub-Antarctic than in boreal forests. Therefore, compared to North America, the seasonality of temperature regimes and the proportion of migratory birds are much less pronounced in South American high-latitude forests, highlighting major climatic and ecological contrasts between temperate and subpolar forests of both hemispheres.