S. Poncet, K. Passfi eld, A. Kuepfer and M.A. Tabak Poncet, S.; K. Passfi eld, A. Kuepfer and M.A. Tabak. The eff ect of Norway rats on coastal waterbirds of the Falkland Islands: a preliminary analysis The effect of Norway rats on coastal waterbirds of the Falkland Islands: a preliminary analysis S. Poncet1, K. Passfi eld2, A. Kuepfer3 and M.A. Tabak4,5 1Antarctic Research Trust, P.O. Box 685, Stanley, Falkland Islands. <
[email protected]> 2Island LandCare, P.O. Box 538, Stanley, Falkland Islands. 3Department of Natural Resources, Falkland Islands Government, Stanley, Falkland Islands. 4Quantitative Science Consulting, LLC, 765 North 10th St., Laramie, WY 82072 USA. 5Department of Zoology & Physiology, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071 USA. Abstract The Falkland Islands have been aff ected by anthropogenic-induced habitat modifi cation including introduction of invasive species and grazing by livestock. Introduced Norway rats are known to have a large eff ect on native Falklands passerines but their eff ect on other native birds has not been explored. We investigated the eff ects of several environmental variables, including the presence of Norway rats and chronic grazing by livestock, on an assemblage of 22 species of coastal waterbirds by comparing species richness and relative abundance of birds among 65 rat-infested islands, 29 rat- eradicated islands and 76 historically rat-free islands. Bird count data from 299 km of coastline were used to estimate relative bird abundance, expressed as the number of individuals per kilometre of coastline for each species. Our study provided three key results.