Chapter 4: Nesting Chronology of the Marbled Murrelet

Abstract

We compiled 86 breeding records of eggs, downy young,and fledgling Marbled Murrelets (Brachyramphus marmoratus) for which the fledging date could be estimated. Records were collected from California (n = 25), Oregon (n = 13), Washington (n = 13), British Columbia (n = 23), and Alaska (n = 12). The number of young fledging increased rapidly from 6 June to 19 July and peaked by the 10-day period beginning 19 July. A second peak in the number of young fledged was observed for the 10-day period beginning 18 August, with a rapid decrease in late August and early September. From these results, a gradual accumulation of fledglings on the ocean would be observed from 30 May until 16 September. By 27 August, only 84 percent of the juveniles in a given year would be expected to be counted at sea. In California and Oregon, it is likely that two distinct periods of breeding activity result from some proportion attempting to lay a second clutch, or pairs renesting after nesting failure. The breeding season appears to be much longer and less synchronous than that of many other members of the alcid family. We conclude that egg-laying and incubation spanned a long period, beginning 24 March and ending 25 August, with the nestling period beginning 23 April and ending with a fledging record on 21 September, a breeding period of 182 days.

Parent Publication

• Ecology and conservation of the Marbled Murrelet

Citation

Hamer, Thomas E.; Nelson,S. Kim. 1995. Chapter 4: Nesting Chronology of the Marbled Murrelet. 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 SouthwestResearch Station, Forest Service, U.S. Department of Agriculture; p. 49-56