PARENT SESSION
Oral Session #3: Conservation Ecology: Threatened and Endangered Species.
Presiding: J. Lawler
Monday, August 5. 8:00 AM to 11:30 AM. Graham Meeting Room, TCC.
Refining marbled murrelet habitat use patterns and detecting population trends using radar.
Bigger, David*,1, Courtney, Steven1, Chinnici, Sal2, 1 Sustainable Ecosystems Institute, Portland, OR2 Scotia Pacific Company LLC, Scotia, CA
ABSTRACT- To effectively manage and contribute to the recovery of the marbled murrelet (Brachyramphus marmoratus), a federally listed seabird, a better understanding of inland nesting habitat use and better methods for detecting population trends are needed. Currently, there is no agreement on how to evaluate relative use or quality of nesting habitat. Further, although marbled murrelets are monitored using at-sea and inland audio-visual surveys, the extent that these approaches can detect population trends is not clear. Recent studies have found that radar is an extremely effective tool for detecting marbled murrelets commuting to their nests. In northern California, we conducted simultaneous radar and audio-visual surveys across a wide range of habitats and environmental conditions to explore how the detectability of murrelets may vary across habitats. We also explored the utility of radar to study murrelet abundance. Using radar, we found that murrelet abundance was greatest near ancient redwood habitat compared to partially harvested old growth stands. Further, murrelets were less visible to audio-visual surveyors in closed canopy habitats. Simulation results predict that radar methods were more likely to detect a 5% annual population decline within five years compared to the at-sea and inland audio-visual survey methods. Finally, we discuss how this information may refine our understanding of marbled murrelet behavior and how it may help land managers identify nesting areas most important for the marbled murrelet conservation.
KEY WORDS: marbled murrelet, threatened, radar, habitat use