Chapter 26 



Mortality of Marbled Murrelets Due to Oil Pollution 

 in North America 



Harry R. Carter 1 



Katherine J. Kuletz 2 



Abstract: Mortality of Marbled Murrelets (Brachyramphus 

 marmoratus) due to oil pollution is one of the major threats to 

 murrelet populations. Mortality from- large spills and chronic oil 

 pollution has been occurring for several decades but has been 

 documented poorly throughout their range; it probably has con- 

 tributed to declines in populations, in conjunction with loss of 

 nesting habitat and mortality in gill nets. The 1989 Exxon Valdez 

 oil spill in Alaska caused the largest single mortality of murrelets 

 (about 8,400 birds) in the world and contributed to decline in 

 murrelet populations in Prince William Sound. Due to inadequate 

 baseline data, low recovery of oiled carcasses, and other factors, 

 the full impacts of this extensive mortality have not been deter- 

 mined. Restoration activities have included acquisition of murrelet 

 nesting areas in old-growth forests in southcentral Alaska. Similar 

 acquisition of old-growth forests will occur as restoration for 

 mortality from the 1986 Apex Houston oil spill in California. 

 Future oil spills will continue to threaten the viability of small, 

 declining populations, especially in California, Oregon and Wash- 

 ington where a single large spill could extirpate an entire popula- 

 tion. Efforts must be expanded to: better document mortalities 

 during large and small spills, develop better baseline data to assess 

 impacts, identify old-growth forests for acquisition for restoration, 

 and reduce oil pollution. 



Large oil spills have killed millions of seabirds around 

 the world in this century, as recently demonstrated during 

 the 1989 Exxon Valdez spill in Alaska (Ford and others 

 199 la, Piatt and Lensink 1989, Piatt and others 1990a). In 

 particular, oil pollution poses a significant threat to Marbled 

 Murrelets (Brachyramphus marmoratus) in Alaska, British 

 Columbia. Washington, and California (Carter and Morrison 

 1992, King and Sanger 1979, Marshall 1988a, Sealy and 

 Carter 1984. Wahl and others 1981). Large numbers of 

 Marbled Murrelets were killed during the Exxon Valdez 

 spill, and this has increased concerns. Large oil spills result 

 periodically from: oil tanker and barge mishaps (groundings, 

 collisions, explosions, accidental spillages); similar mishaps 

 by other large ocean-going vessels; offshore oil wells (well 

 blow-outs, accidental spillages); unloading and loading cargo 

 from onshore and offshore facilities; and onshore facility 

 spills that enter the ocean. In addition, small oil spills occur 

 frequently in many populated areas due to cleaning of tanks 

 at sea. bilge pumping and smaller accidental spills. All types 

 of boats and marine transportation vessels may be involved. 



1 Wildlife Biologist. National Biological Service, U.S. Department of 

 the Interior. California Pacific Science Center, 6924 Tremont Road. Dixon, 

 CA 95620 



2 Wildlife Biologist, U.S. Fish and Wildlife Service. Migratory Bird 

 Management, 1011 East Tudor Road. Anchorage. AK 99503 



Other forms of marine pollution that may affect seabirds are 

 considered by Fry (this volume). 



Impacts of large oil spills on seabirds in California, 

 Oregon, and Washington have been well-documented during 

 the last 25 years, and sporadically in earlier years. Wide- 

 spread concern about the effects of oil spills on seabirds 

 along the west coast developed after the 1969 Santa Barbara 

 and 1971 San Francisco oil spills in California and smaller 

 spills in Washington. These spills followed similar events in 

 Europe such as the 1967 Torrey Canyon spill in the western 

 English Channel (Bourne and others 1967). Since the 1970s, 

 the documentation of oil spills and their impact on seabirds 

 has been much improved. 



Impact assessment is now formalized within Natural 

 Resource Damage Assessment (NRDA) legislation. When 

 possible, the numbers of birds affected are enumerated and 

 impacts at the population level are determined. Impacts 

 include: the direct deaths of birds found dead on shore; 

 deaths of birds found alive on shore and taken to rehabilitation 

 centers; deaths of birds at sea and on shore that are not 

 directly enumerated; reductions in numbers of breeding birds; 

 reductions in breeding range; reduced breeding success; and 

 the sublethal effects of oiling for birds that survived initial 

 oil contamination whether rehabilitated or not. 



When the full impacts of oil pollution are considered, 

 lethal and sublethal impacts may have profound effects on 

 local populations, especially when oil mortality acts in concert 

 with other anthropogenic and/or natural factors affecting 

 populations (Piatt and others 1991, Swartzman and Carter 

 1991, Takekawa and others 1990). However, population 

 impacts are often difficult to demonstrate because they usually 

 require detailed pre-event baseline data, careful injury 

 determination, and detailed follow-up data after the event. 



In this paper, we review documentation of mortality of 

 Marbled Murrelets due to oil pollution throughout their range 

 in North America. In particular, we have focused on providing 

 a summary of mortality and restoration efforts after the 1989 

 Exxon Valdez spill in Alaska and details of mortality for 

 several smaller spills in California, Oregon, Washington, 

 and British Columbia, where the species in now listed as 

 threatened. Information for the three southern states was 

 collated for the Marbled Murrelet Recovery Plan (U.S. Fish 

 and Wildlife Service, in press). 



Exxon Valdez Oil Spill 



The largest single event of Marbled Murrelet mortality 

 from oil pollution in North America was the Exxon Valdez 

 oil spill in Prince William Sound, Alaska. On 24 March 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



261 



