Monitoring Rock Ptarmigan (Lagopus muta) populations in the Western Aleutian Islands, Alaska

Résumé

Knowledge of population fluctuations of Aleutian Islands Rock Ptarmigan (Lagopus muta) is limited because of isolation and access. We reviewed the available but limited data on ptarmigan counts on islands in North America and evaluated the use of point counts to estimate changes in apparent numbers of Rock Ptarmigan on three islands (Adak, Amchitka, and Attu) in the Western Aleutian Islands in Alaska. We developed a standardized protocol to count numbers of Rock Ptarmigan (males and females) seen and/or heard on 5-minute point counts at 0.8 km intervals along marked global positioning system routes on Adak (2015–2017), Amchitka (2015), and Attu (2015) islands. Apparent densities based on Rock Ptarmigan seen and/or heard at 98 stops on 10 routes varied and were highest (1.9 birds per stop in 2015, 1.4 in 2016, and 1.0 in 2017) on Adak, lower (0.4 birds per stop) on Amchitka, and lowest (0.0 birds per stop) on Attu in late May–early June 2015. These island populations represent three subspecies and unique conservation units. Continuation of point-count surveys of these three subspecies in future years will provide baseline data over time and lead to a better understanding of any fluctuations in and synchrony among Rock Ptarmigan populations on these islands. This information is necessary for both theoretical (how are ptarmigan breeding populations regulated on islands) and practical reasons (identifying the optimal period for possible translocation to islands where ptarmigan were extirpated by introduced Arctic Fox [Vulpes lagopus]).