Distribution of the Marbled Murrelet in Western Oregon
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DISTRIBUTION OF THE MARBLED MURRELET IN WESTERN OREGON Final Report to the Oregon Department of Fish and Wildlife (Contract 89-9-02) Submitted May 1990 DISTRIBUTION OF THE MARBLED MURRELET IN WESTERN OREGON CONTRACTOR Oregon Nongame Wildlife Research Program Oregon Department of Fish and Wildlife SW First Street Portland, OR 97207 INVESTIGATOR S. Kim Nelson Oregon Cooperative Wildlife Research Unit Department of Fisheries and Wildlife Oregon State University Corvallis, Oregon 97331-3803 ACKNOWLEDGMENTS This study was funded by the Oregon Department of Fish and Wildlife Non- game Wildlife Research Program (Contract 89-9-02), in cooperation with the U.S. Forest Service, Bureau of Land Management, National Council of the Paper Industry for Air and Stream Improvement and the National Fish and Wildlife Foundation. The research was conducted under the auspices of the Oregon Cooperative Wildlife Research Unit at Oregon State University. I owe a special thanks to Bill Haight, Bill Neitro, Wayne Logan, Holt Holthausen, and Charles Meslow for their support and guidance. This study could not have been a success without the tremendous efforts of my 10 research assistants and volunteers. I extend a sincere thanks to Jody Carter, April Claggett, Sally Claggett, Tim Dwyer, Janet Hardin, Barbara Maier, Jim McGinn, Michael Pope, John Sterling, and Will Wright. In addition, I am grateful to the following U. S. Forest Service, Bureau of Land Management, Oregon Department of Fish and Wildlife, U.S. Fish and Wildlife, Oregon Department of Forestry, and Oregon State Parks biologists and resource specialists for providing maps, materials and logistical assistance: Carol Bickford, Robin Brown, Connie Frisch, Sarah Greene, Scott Hayes, Sallie Jacobsen, Joe Lint, Wayne Logan, Roy Lowe, Steve Lucas, Larry Mangen, Kim Mellen, Randy Miller, Clint Smith, Janet Stein, Charlie Thomas, Norma Vangrunsven, Heide Vogt, Lou Wallenmeyer, Lee Webb, Margie Willis and Joe Witt. I also thank Richard Gustafson of Cavenham Forest Industries and Kent Boring of Stimson Lumber Company for allowing us access to their lands on the north coast for conducting surveys. DISTRIBUTION OF THE MARBLED MURRELET IN WESTERN OREGON INTRODUCTION The Marbled Murrelet (Brachyramphus marmoratus) is a small, robin-sized seabird that inhabits near-shore coastal waters and inland older-aged (>80 yrs) coniferous forests of the Pacific Northwest. Before 1989, this alcid was located up to 47 km from the ocean at 46 inland sites in western Oregon (40 in the central Coast Range and 6 in the southern Coast Range) (Nelson 1989, Nelson et al. in review). In addition, four historic records of adults and juveniles discovered at inland sites in the central Coast Range were known (Marshall 1988, Nelson et al. in review).. Despite these inland sightings, little was known about the overall distribution and specific habitat preferences of the Marbled Murrelet in Oregon. Knowledge of the current distribution of this species is important for assessing impacts of land management on their future abundance and distribution in Oregon, and related cumulative impacts on northern California and Washington populations. In 1988, research on Marbled Murrelets included creating and testing inventory techniques (Paton and Ralph 1988, Nelson 1989). Effective road transect methodologies were developed for determining the presence and absence of this alcid in inland coniferous forests. Using these methodologies, a project was undertaken in spring and summer of 1989 to meet the following objectives: (1) determine the presence and absence of Marbled Murrelets in 2 selected study sites in the Oregon Coast Ranges, (2) describe large scale habitat and geographic associations in areas where murrelets are detected, (3) describe habitat associations in potential nest areas, and (4) collect information on murrelet behavior. 3 STUDY AREA AND METHODS The study area was located in the Oregon Coast Ranges between the Columbia River and the California border. Lands within this area are administered by the U.S. Forest Service, Bureau of Land Management, Oregon Department of Forestry, Oregon State Parks, County Parks, U.S. Fish and Wildlife Service, private timber companies, and individuals. The Oregon Coast Ranges were divided into 9 equal-sized blocks (165 by 20 km): 3 north to south based on latitude, and 3 east to west based on distance from the coast (maximum distance 60 km) (Figure 1). A total of 137 road transects were established within the study area (Figure 2, Appendix 1). Eight to ten (primarily nine) sampling stations, spaced at a minimum of 0.5 km intervals, were located along each transect (Figure 3). Location of transects, distance between stations, and transect length varied with the distribution and abundance of appropriate habitat. For the purpose of this study, appropriate Marbled Murrelet habitat was defined as trees > 25 cm in diameter (DBH). Sampling stations were therefore established in coniferous forest stands (>2 ha in size) of 3 tree size classes: 25-45 cm, 46-81 cm, and >82 cm (Hall et al. 1985). Open pole-sapling stands and clearcuts were not surveyed. I assumed that murrelets would not nest in these habitat types based on previous research on this species (Marshall 1988). Within each block, I attempted to establish an equal number of transects and stations in the 3 tree size class. However, a long history of natural (fire) and man-made disturbances (logging) in the Oregon Coast Ranges limited 4 the abundance of stands with trees >82 cm DBH. The distribution of stations by tree size class generally reflected availability in the Coast Ranges; most transects were located adjacent to mature stands (Appendix 2). In addition, more transects were located along the central coast and in close proximity to the coast, where appropriate murrelet habitat was relatively common (Appendices 3 and 4). A method for surveying Marbled Murrelets from road transects was developed by Paton et al. (1989). Similar survey techniques were implemented to facilitate comparisons with other studies. However, each transect was visited 4 times between 15 May and 15 August, instead of 3, to improve conclusions regarding presence and absence. On alternate surveys, observers ran transects in reverse order (visit 1: stations 1-10, visit 2: stations 10- 1, repeat) to avoid any time of day biases. Surveys began 45 minutes before, and continue until 75 minutes after, official sunrise (determined from tables constructed by the Oregon State University Climatic Research Institute). Each station was surveyed for 10 minutes. Information collected at sampling stations where murrelets were detected included: time of observation, number of birds detected, type of detection (audio, visual, both), number of vocalizations, direction and distance to the observation, length of observation, and murrelet behavior (flight patterns, height of bird, direction of flight). Definitions Detection: the visual or auditory observation of 1 or more murrelets acting in a similar manner at a given point in time. 5 Presence: hearing or seeing murrelets on at least one visit from at least one station. Percent Occurrence: the percent of transects or stations at which murrelets were detected at least once. Flight Corridor: a river basin or drainage used by murrelets on flights between inland forests and the ocean. Potential Nest Area: a forest stand where murrelets were observed flying into or out of the canopy, landing in trees, nesting or calling from stationary locations. Data Analysis The percent occurrence of murrelets was calculated within each tree size class, and in relation to latitude and distance to the coast. Differences in percent occurrence and number of detections within each category were compared using Chi-square analysis and Kruskal-Wallis ANOVA (analysis of variance), respectively (SAS Institute, Inc. 1987). The percent of habitat in each tree size class along each transect was correlated with the presence of murrelets using Mann-Whitney U-tests (SAS Institute, Inc. 1987). I used contingency table analysis (SYSTAT, Inc. 1984) to determine which geographic or habitat variable (latitude, distance from the coast, tree size class) or combination of variables had the most effect on murrelet presence. The procedure involved a hierarchical partitioning of a four factor log-linear model into individual and interactive terms. The most important variable affecting murrelet presence was chosen based on the significance of the G2 statistic, while controlling for all other possible interactions (see Fienberg 1980 for further details). 6 Vegetation and topographic features of potential nest sites were compared to an equal number of random sites to determine habitat selection. The random sites were selected with a random number generator from the pool of stations along road transects where murrelets were not detected. Habitat characteristics of these stands were summarized through analytical stereo plotter aerial photo (1986, black and white, 1:31,000) interpretation. Variables collected in each area included stand age (yrs), stand size (ha), tree species composition, tree height (m), tree diameter (cm, DBH), canopy cover (%), aspect(°), slope (%), elevation (ridge and drainage; m), and distance from the coast (km). Tree height and diameter were also determined for remnant trees (old-growth trees that survived previous disturbances) when present. Mann Whitney U-tests were used to compare mean habitat characteristics of nest and random stands (SAS Institute, Inc. 1987).