Chapter 35: Productivity of marbled murrelets in California from observations of young at sea

Abstract

We designed and tested an intensive survey method in 1993 to identify juvenile Marbled Murrelets (Brachyramphus marmoratus) at sea. From this, we used the percent of juveniles seen in the sample as an index of productivity of murrelets along the California coast. We found 2.2 percent of the population sampled were juveniles, similar to our estimates in 1989—1992 of 3 percent from less stringent survey methods in this area. Percent of juveniles in the 1993 sample ranged from almost 6 percent in late June to none in mid-August and September. Juveniles were as often alone as in a group with 1 or 2 adults, and showed a similar distribution in distance from shore as adults. We found that some adults were molting into basic plumage as early as 21 June, with three-fourths in molt by mid-August. Therefore, during September, most birds were unidentifiable to age since most appeared to be in basic plumage unless they flapped their wings to expose molting primaries or markings on the lower breast or belly.

Parent Publication

• Ecology and conservation of the Marbled Murrelet

Citation

Ralph C. John; Long, Linda L. 1995. Chapter 35: Productivity of marbled murrelets in California from observations of young at sea. 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. 371-380