Chapter 8: Nest Success and the Effects of Predation on Marbled Murrelets

Abstract

We summarize available information on Marbled Murrelet (Brachyramphus marmoratus) productivity and sources of mortality compiled from known tree nests in North America. We found that 72 percent (23 of 32) of nests were unsuccessful. Known causes of nest failure included predation of eggs and chicks (n = 10), nest abandonment by adults (n = 4), chicks falling from nests (n = 3), and nestlings dying (n = 1). The major cause of nest failure was predation (56 percent; 10 of 18). Predators of murrelet nests included Common Ravens (Corvus corax) and Steller’s Jays (Cyanocitta stelleri); predation of a nest by a Great Horned Owl (Bubo virginianus) was also suspected. We believe that changes in the forested habitat, such as increased amounts of edge, are affecting murrelet productivity. Successful nests were significantly further from edges ( x = 155.4 versus 27.4 m) and were better concealed ( x = 87.2 versus 67.5 percent cover) than unsuccessful nests. The rate of predation on Marbled Murrelet nests in this study appear higher than for many seabirds and forest birds. If these predation rates are representative of rates throughout the murrelet’s range, then the impacts on murrelet nesting success will be significant. We hypothesize that because this seabird has a low reproductive rate (one egg clutch), small increases in predation will have deleterious effects on population viability. Rigorous studies, including testing the effects of various habitat features on recruitment and demography, should be developed to investigate the effects of predation on Marbled Murrelet nesting success.

Parent Publication

• Ecology and conservation of the Marbled Murrelet

Citation

Nelson, S. Kim; Hamer, Thomas E. 1995. Chapter 8: Nest Success and the Effects of Predation on Marbled Murrelets. 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. 89-98