Title: At-Sea Abundance and Distribution of Marbled Murrelets in the Naked Island Area, Prince William Sound, Alaska, in Summer 1991 and 1992
Project Year and Number: 1992: R015-1
Other Fiscal Years and Numbers for this Project: 1992: R015-2
Principal Investigator (PI): Kathy Kuletz, US Fish & Wildlife Service
Research Location: Prince William Sound
Restoration Category: Damage Assessment
Abstract: The marbled murrelet (Brachyramphus marmoratus) is a small seabird which largely depends on old growth forests for nesting (Binford et al. 1975, Marshall 1988, Manley and Kelson 1991, 1992, Quinlan and Hughes 1990, Singer et al. 1991, 1992, Nelson et al. 1992). The species currently is being considered for threatened or endangered status throughout most of its range, excluding Alaska. Prince William Sound is one of three major population centers of the marbled murrelet in Alaska (Mendenhall 1988). This population suffered substantial direct mortality from the Exxon Valdez oil spill. Based on an eight percent chance of carcass recovery (Ford et al. 1991) an estimated 9,570 murrelets were directly killed. In Prince William Sound, marbled murrelets were 12% of retrieved carcasses, which is proportionally more of the seabird population than the numbers at risk at the time of the spill (Piatt et al. 1990). Additionally, petroleum hydrocarbon contamination has been found in the livers of unoiled murrelets collected in 1989 in oiled areas of the Prince William Sound (Kuletz 1992a). Murrelets collected in unoiled areas of Prince William Sound after the spill were uncontaminated.
The Prince William Sound marbled murrelet population has declined significantly, from approximately 300,000 in 1972 to 100,000 in 1989-1991 (Laing 1991), thus it is difficult to determine the contribution of the Exxon Valdez oil spill to this decline. There was no significant difference in murrelet counts between oiled and unoiled shoreline in the Prince William Sound boat surveys or the Naked Island area surveys. Since only about 25% of the murrelets occupy waters within 200 m from shore (Laing, unpubl. data), and murrelets are highly mobile in foraging, it is unlikely that an oiling effect could be detected using the current methods of analysis.
The limited data available on murrelet breeding biology suggests that their reproductive success is quite low (Hamer and Cummins 1991, Kuletz 1992b, Nelson et al. 1992, Singer et al. 1991, 1992). Murrelets face additional impacts from loss of nesting habitat due to logging, which could threaten natural recovery. Protection of forested nesting habitat through acquisition is one potential approach for aiding recovery of murrelets in the oil spill area.
Integral to this approach is the ability to identify appropriate habitat for protection. However, because so little is known about the murrelet's habitat requirements or its breeding distribution, further efforts are needed to achieve this goal. Two primary components are intimately linked in identification of appropriate sites - what are the characteristics of murrelet nesting habitat and which potentially suitable areas in the oil spill area are being used by the species? Documenting areas used by nesting murrelets is elusive because nests are generally difficult to find. This study will attempt to answer these questions.
An attempt will be made to locate a relatively large number of murrelet nests in an area in which ground search techniques have proven to be an effective means for finding nests (Kuletz 1992b). At these sites critical elements of nesting habitat will be quantified and behaviors, vocalizations and activity patterns associated with nesting will be defined. These results will be used to establish criteria for inferring use of an area by nesting murrelets, for refining nest search techniques and for determining nesting habitat requirements (Objective 1). Censuses will also be conducted at various locations in Prince William Sound to locate high use areas. The results from known nest sites will then be used to interpret the significance of murrelet activity (Objective 2).
Marbled murrelets typically forage in shallow near shore waters during the breeding season. This area is particularly vulnerable to oil pollution and human disturbance. Consequently, proper management of the adjacent marine environment is also important in protecting murrelet habitat. Thus, delineation of near shore murrelet distribution relative to nesting areas has been included in Objectives 1 and 2. The results of this study will be integrated with other sources of data on murrelets in the Exxon Valdez oil spill area (Objective 3). These data will be analyzed, synthesized and used to corroborate nesting requirements and appropriate protection measures.
Completion of this phase of the study in 1992 will result in knowledge of murrelet nesting habitat requirements and identification of uplands with the most potential for murrelet nesting. This study will also provide guidelines for identifying nesting habitat throughout the oil spill area.
Prince William Sound
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Proposal: PDF Not Available
Funding Recommendations: View
Funding Detail For: 1992
Quarterly Project Tasks For: 1992
Annual Report: 1992: Not Applicable
Final Report: View
Publications from this Project: None Available
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|1992: R015-2||Not Available||