Carter and Kuletz 



Chapter 26 



Mortality Due to Oil Pollution 



and (3) some observers may not have been able to identify 

 Marbled Murrelet carcasses (especially decomposed 

 carcasses) (Stenzel, pers. comm.). Only one of the 23 murrelets 

 found during this program was determined to be oiled. 

 However, the degree of oiling may be underestimated, due 

 to the advanced state of decomposition of some carcasses 

 (Stenzel, pers. comm.). In Washington, beached bird surveys 

 were conducted between 1978-1979 for inland marine areas 

 (Speich and Wahl 1986). Only one unoiled Marbled Murrelet 

 was recovered dead on beaches out of a total 110 birds 

 examined. Between January 1982 and December 1986, outer 

 Washington coast areas (especially in the vicinity of Grays 

 Harbor) also were surveyed by Lippert (Speich, pers. comm.). 

 A total of five murrelets (two adults and three unknown age) 

 were found. Only one oiled adult was found on Ocean Park 

 Beach, Washington (see 1984 Mobiloil above). Both of these 

 beached bird programs were conducted between the early 

 1970s and mid 1980s when large and medium oil spills 

 occurred less frequently (Burger and Fry 1993). Thus, the 

 low occurrence of oiled murrelets on these surveys may 

 reflect low incidence of oil pollution as well as low recovery 

 of oiled and unoiled murrelet carcasses. Burger (1992) 

 conducted beached bird surveys between 1987-1991 on the 

 southwest coast of Vancouver Island, British Columbia. 

 Marbled Murrelets were not reported specifically. Small 

 alcids were lumped into one category (of which few were 

 recovered in any case). 



Summary and Recommendations 



It is difficult to assess the impacts of oil spills and other 

 marine pollution on Marbled Murrelets because of inadequate 

 baseline data, and poor documentation of post-spill damages. 

 For example, even though reasonable population estimates 

 were available in Prince William Sound, 17 years separated 

 pre-spill and post-spill surveys. Klosiewski and Laing (1994) 

 determined that, given the low number of baseline survey 

 years, their tests only had a 20-40 percent probability (based 

 on Monte Carlo runs) of detecting a 50 percent decline in 

 population size of Marbled Murrelets in Prince William 

 Sound. In particular, low recovery rates of murrelets after 

 pollution events must result in part from: (1) improper 

 identification of murrelet carcasses that resemble other small 

 alcids; (2) undercounting of carcasses on beaches due to 

 small carcass size, incomplete coastal coverage, and burial 

 in beach substrates; (3) high rates of carcass removal by 

 predators on shore and at sea; and (4) carcass loss due to 

 sinking at sea. Efforts are underway to improve the rate of 

 recovery of murrelet carcasses during large oil spills, 

 especially by the California Department of Fish and Game 

 (Kelly, pers. comm.) and Washington Department of Fish 

 and Wildlife (Warheit, pers. comm.). 



However, seabird mortality from small spills is often 

 not assessed. Greater efforts should be expended to investigate 

 all spills for their impacts on Marbled Murrelets. In addition, 



greater coordination is required between wildlife care centers 

 and government agencies for documenting live and dead 

 murrelets sporadically found on shore in small numbers. In 

 Washington, the Adopt A Beach program may recover such 

 oiled carcasses during regular beach surveys although none 

 have been found from 1988-1993 (Silver, pers. comm.). In 

 California, a group such as the International Wildlife 

 Rehabilitation Council could coordinate better documentation 

 and reporting of oiled murrelets turned into wildlife care 

 centers of various affiliations (e.g., Society for the Prevention 

 of Cruelty to Animals, International Bird Rescue, etc.). In 

 addition, the Beach Watch program may encounter oiled 

 murrelets through regular beach surveys within the Gulf of 

 the Farallones and Monterey Bay National Marine Sanctuaries 

 which encompass the central California population of Marbled 

 Murrelets (Rolleto, pers. comm.). Birds found on beach 

 surveys or interned in centers should be preserved for later 

 examination or to have their identification confirmed. Oil 

 samples from such birds also may link mortality to specific 

 sources. Also, rehabilitation efforts for oiled murrelets must 

 be improved by conducting physiological, wildlife health, 

 and captive care research on oiled murrelets. 



Better baseline data and monitoring (before, during and 

 after the pollution event) is needed for at-sea population size 

 and distribution during the non-breeding and breeding seasons. 

 This task is immense, especially in Alaska and British 

 Columbia, but is critical to documenting injury and devising 

 restoration activities. As populations dwindle in size, it will 

 be important to attempt to prevent all mortality possible, 

 even if this process is costly and has only moderate success. 



We feel that a detailed assessment of the threat of oil 

 pollution to Marbled Murrelets throughout their range in 

 North America is required by analyzing data on: (1) the 

 location, size and frequency of oil spills; (2) the distribution 

 and abundance of Marbled Murrelets at sea; (3) the routes of 

 tanker and other shipping traffic along the coast; and (4) the 

 amount of oil transported along the coast by various means 

 (Burger 1992; USDI Fish and Wildlife Service, in press). 

 Databases with some of the above spill and NRDA information 

 are being developed from California to Alaska (Kelly, pers. 

 comm.; Oman, pers. comm.). With these databases, future 

 in-depth analyses should be conducted to indicate the overall 

 threat of oil pollution to Marbled Murrelets over the long 

 term and to devise methods to reduce oil mortality. 



Oil pollution has had significant impacts on murrelet 

 populations in Prince William Sound, central California, 

 and western Washington. However, these effects have 

 probably been felt only sporadically by local populations. If 

 murrelet populations were in better health, oiling mortality 

 might be naturally recoverable within several years to decades, 

 depending on the size and nature of the mortality. However, 

 when oiling mortality is considered as a cumulative effect 

 with other anthropogenic factors and affects small, declining 

 populations of murrelets, the relative effects of oil pollution 

 will become greater and recovery may not be possible (Piatt 



268 



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



