Treesearch

Over the past decade, the Marbled Murrelet has become a focus of much controversy. It was listed as threatened in Washington, Oregon, and California by the U.S. Fish and Wildlife Service in February 1993. In order to aid the various agencies with management, the Marbled Murrelet Conservation Assessment was formed to bring together scientists, managers, and others to gather all the available data on this small seabird. This volume of research is the culmination of that effort. In this chapter, we integrate the results of the investigations and summaries on the past history, present status,...

To determine the abundance and distribution of Marbled Murrelets, aerial surveys of the Oregon coast, Washington outer coast, and shores of the western Strait of Juan de Fuca were conducted in August/September 1993. Based on these marine surveys, abundance estimates are established for Oregon (6,400-6,800 birds) and the waters surveyed in Washington (3,400-3,600 birds). A comparison of these estimates to those established by other surveys indicates that boat-based surveys may give higher estimates of murrelet abundance, and that population size has probably not decidedly changed over the...

About 45,000-50,000 Marbled Murrelets (Brachyramphus marmoratus) breed in British Columbia, with some birds found in most parts of the inshore coastline. A review of at-sea surveys at 84 sites revealed major concentrations in summer in six areas. Murrelets tend to leave these breeding areas in winter. Many murrelets overwinter in the Strait of Georgia and Puget Sound, but the wintering distribution is poorly known. Aggregations in summer were associated with nearshore waters (

Mortality of Marbled Murrelets (Brachyramphus marmoratus) due to accidental capture in gill nets is one of the major threats to murrelet populations. Gill-net mortality of murrelets throughout their range has been occurring for several decades and probably has contributed to declines in populations, in conjunction with loss of nesting habitat and mortality from oil spills. Gill-net mortality has been best studied in Prince William Sound, Alaska, and in Barkley Sound, British Columbia. However, gill-net fishing occurs widely and it is likely that: (1) several thousand to tens of thousands...

Marbled Murrelets (Brachyramphus marmoratus) have been shown to be dependant upon old-growth forests for nesting habitat. These forests have declined over the last century as they are cut for human use. This paper reviews the current status of old-growth forests along the west coast, in both the United States and Canada.

Ship-based surveys conducted throughout Alaska during the 1970’s and 1980’s, and more recent small boat surveys conducted in the northern Gulf of Alaska, suggest that about 280,000 murrelets reside in Alaska during summer. Most Marbled Murrelets are concentrated offshore of large tracts of coastal coniferous forests in southeast Alaska, Prince William Sound, and the Kodiak Archipelago. About 1– 3 percent of murrelets breed wholly outside of forested areas in Alaska, and these presumably all nest on the ground. At sea, murrelets tend to occupy sheltered waters of bays, fiords, and island...

A demographic model of the Marbled Murrelet is developed to explore likely population trends and factors influencing them. The model was structured to use field data on juvenile ratios, collected near the end of the breeding season and corrected for date of census, to estimate fecundity. Survivorship was estimated for the murrelet based on comparative analyses of allometric relationships from 10 species of alcids. Juvenile ratios were generally low, and were higher for counts made from shore or in kelp beds (typically 10 percent) than conducted offshore (

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...