Investigations of insular populations of Rock Ptarmigan (Lagopus muta) in Alaska over time are uncommon. We documented changes in spring density of Evermann's Rock Ptarmigan (L. m. evermanni) on a portion of Attu Island, Alaska, from 2003 through 2009. Populations were 8.5 birds/km2 in 2003, decreased by approximately one-half in 2004 (3.8 birds/km2), and continued to decrease in 2005 (1.9 birds/km2), 2006 (0.8 birds/km2), and 2007 (0.6 birds/km2), reaching a low of 0.3 birds/km2 in 2009. The overall decrease from 2003 through 2007, and 2009 was approximately 97%. We conclude the most reasonable explanation for the decline was poor recruitment (90% decrease from 2003 to 2006) of young (subadult = yearling) to the spring population, possibly related to natural cycling of the population. We could not identify specific factors to explain the low recruitment.
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Vol. 95 • No. 1