Optimal habitat for Austral Rail Rallus antarcticus and the problem of American Mink and cattle management

Austral Rail (Rallus antarcticus), a globally vulnerable species, inhabits wetlands in Argentinean and Chilean Patagonia, a rare habitat in the region, which occupies only a 1.13% of its surface. The invasive American Mink (Neovison vison) and cattle management including rush burning and harvesting have been suggested as threats to Austral Rail populations, and some characteristics of its habitat were described at a minor scale. At a wetland scale, we related the occupancy and relative abundance of the rail with different rates and combinations of these threats. At a finer scale, we related the rail´s presence to rush features (height and density), bird community and presence of water. We studied five rush lands located in ranches with and without cattle management in Santa Cruz province, Argentina, between December 2015 and April 2016. We used Occupancy Models and GLM. Occupancy and relative abundance were higher in rush lands without mink or cattle management. In rush lands with only cattle management both parameters declined and where mink was present no rails were detected. At the finer scale, the best model for rail’s presence included the size of the rushes (with a strong association to medium size rushes, Z=2.073, p<0.05) and rush density (avoiding low density rushes, Z=2.037, p<0.05). Here we present for the first time, an association between environmental features and this rail’s occupancy and abundance. Wetlands that favor Austral Rail conservation seems to be those least impacted by humans, especially those without mink, and those with tall and dense rushes.