Chapter 15: Inland Habitat Suitability for the Marbled Murrelet in Southcentral Alaska

Abstract

The majority of Marbled Murrelets (Brachyramphus marmoratus) nest in Alaska, where they sometimes nest on the ground, and their nesting habitat requirements are not well understood. The inland activity of murrelets was surveyed, and habitat features measured, between 1991 and 1993, in Prince William Sound, Kenai Fjords National Park and Afognak Island, Alaska (n = 262 sites). We used these data to develop statistical models that explain variation in murrelet activity levels and predict the occurrence of occupied behaviors (indicative of nesting), based on temporal, geographic, topographic, weather, and habitat characteristics. Multiple regression analyses explained 52 percent of the variation in general murrelet activity levels (P < 0.0001). The best model included survey date, location relative to the head of a bay, elevation, slope, aspect, percentage of forest cover, tree diameter, and epiphyte cover on tree branches. The highest activity levels were associated with late July surveys at the heads of bays where there was high epiphyte cover on trees. Stepwise logistic regression was used to identify variables that could predict the probability of detecting occupied behaviors at a survey site. The best model included survey method (from a boat, shore, or upland), location relative to the head of a bay, tree diameter, and number of potential nesting platforms on trees. The best predictors for observing occupied behaviors were tree diameter and number of platforms. In a jackknife procedure, the logistic function correctly classified 83 percent of the occupied sites. Overall, the features indicative of murrelet nesting habitat include low elevation locations near the heads of bays, with extensive forest cover of large old-growth trees. Our results were derived from surveys designed to estimate murrelet use of forested habitat and may not accurately reflect use of nonforested habitat. Therefore, caution should be exercised when extrapolating observed trends on a broad scale across the landscape.

Parent Publication

• Ecology and conservation of the Marbled Murrelet

Citation

Kuletz, Katherine J.; Marks, Dennis K.; Naslund, Nancy L.; Goodson, Nike J.; Cody, Mary B. 1995. Chapter 15: Inland Habitat Suitability for the Marbled Murrelet in Southcentral Alaska. In: Ralph, C. John; Hunt, George L., Jr.; Raphael, Martin G.; Piatt, John F., Technical Editors. 1995. Ecology and conservation of the Marbled Murrelet. Gen. Tech. Rep. PSW-GTR-152. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; p. 141-150