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Chapter 5: Marbled Murrelet Chapter 5: Marbled Murrelet Martin G. Raphael, Gary A. Falxa, and Alan E. Burger1 small management areas to an approach based primarily on the designation of fewer large areas, each designed to Introduction conserve functioning late-successional and old-growth In this chapter, we describe expectations of the Northwest ecosystems. These were intended to support multiple Forest Plan (NWFP, or Plan) and review recent science on pairs of northern spotted owls (Strix occidentalis caurina) the ecology and status of the marbled murrelet (Brachy- and murrelets, and to conserve habitat for other species ramphus marmoratus), with an emphasis on the portion associated with older forests. of the species’ range that falls within the Plan area. The The marbled murrelet is a small seabird of the family conservation strategy embodied in the NWFP evolved from Alcidae (fig. 5-1) whose summer distribution along the designation and protection of a large number of relatively Pacific Coast of North America extends from the Aleutian Islands of Alaska to Santa Cruz, California (fig. 5-2). It forages primarily on small fish and krill in the nearshore (0 to 2 mi [0 to 3 km]) marine environment. Unlike other 1 Martin G. Raphael is a research wildlife biologist (retired), U.S. Department of Agriculture, Forest Service, Pacific Northwest alcids, which nest in dense colonies on the ground or in Research Station, 3625 93rd Ave. SW, Olympia, WA 98512; Gary A. Falxa is a wildlife biologist (retired), U.S. Fish and Wildlife Ser- burrows at the marine-terrestrial interface, murrelets nest vice, 1615 Swanson Lane, Eureka, CA 95503; Alan E. Burger is an in more dispersed locations up to 55 mi (89 km) inland. In adjunct professor, University of Victoria, Department of Biology, and a wildlife consultant, P.O. Box 2539, Merritt, BC V1K 1B8. the southern portion of the range, including the Plan area Martin Raphael Martin Figure 5-1—The marbled murrelet is a small seabird of the family Alcidae. 301 GENERAL TECHNICAL REPORT PNW-GTR-966 Binford et al. 1975; Hamer and Cummins 1991; Hamer and Nelson 1995; Hamer et al. 1994; Hébert and Golightly 2006; Quinlan and Hughes 1990; Ralph et al. 1995a; Singer et al. 1991, 1992; Wilk et al. 2016). The marbled murrelet popu- lation in Washington, Oregon, and California nests in most of the major types of coniferous forests (Hamer and Nelson 1995) in the western portions of these states, wherever older forests remain inland of the coast at elevations primarily below the extent of the true fir zone, generally <4,000 ft (1220 m) (table 5-1). Although murrelet nesting habitat characteristics may differ throughout the range of the species, some general habitat attributes are characteristic throughout its listed range, including the presence of nesting platforms, adequate canopy cover over the nest, larger patch size of mature forest, and being within commuting distance Figure 5-2—Range of the marbled murrelet in North America. Map by Terry Sohl from NatureServe data. to the marine environment (Binford et al. 1975, Hamer and Nelson 1995, Nelson 1997, McShane et al. 2004, Ralph et al. 1995b). Because murrelets do not construct nests, they and the area emphasized in this chapter, murrelets typically depend on the availability of platforms, typically tree limbs nest in large coniferous trees in forested areas containing with a moss or other thick substrate, such as piles of needles characteristics of older forests. Throughout the forested por- collected on limbs near a tree bole, sufficiently large for tion of the species’ range, murrelets typically nest in areas laying their single egg and raising a nestling (Nelson 1997, containing characteristics of older forests (Baker et al. 2006; Ralph et al. 1995). Table 5-1—Known inland limits of marbled murrelet nests and occupied sites Inland distance Occupied State/province Nesta site Sources - - - Miles - - - Alaska 33 Nelson et al. 2010, Whitworth et al. 2000 British Columbia 39 41 Jones et al. 2006, Lougheed 1999, Nelson et al. 2010, Ryder et al. 2012 Washington 55 55 D. Lynch, personal communicationb; Ritchie and Rodrick 2002 Oregon 32 47 Alegria et al. 2002; Dillingham et al. 1995; E. Gaynor, personal communicationc; Witt 1998a, 1998b California 24 24 S. Chinnici, personal communicationd; A. Transou, personal communicatione Note: see table on page 338 for metric equivalents. a Includes grounded fledglings and eggshell fragments. b D. Lynch. Personal communication. Fish and wildlife biologist, Washington Department of Fish and Wildlife, 111 Washington Street SE, Olympia, WA 98501. c E. Gainer. Personal communication. Wildlife biologist, U.S. Department of the Interior, Bureau of Land Management, 777 NW Garden Valley Blvd., Roseburg, OR 97471. d S. Chinnici. Personal communication. Forest science manager, P.O. Box 712, Humboldt Redwood Company, Scotia, CA 95565. e A. Transou. Personal communication. Environmental scientist, California Department of Parks and Recreation, North Coast Redwoods District, P.O. Box 2006, Eureka, CA 95502; 707-445-6547; [email protected]. 302 Synthesis of Science to Inform Land Management Within the Northwest Forest Plan Area Individual tree attributes that provide conditions suitable typically found in old-growth and mature forests, but may for nesting (i.e., provide a nesting platform) include large be found in a variety of forest types, including younger branches (ranging from 4 to 32 inches (10 to 81 cm) diameter, forests containing remnant large trees. Since 1996, with an average of 13 inches (33 cm) in Washington, Oregon, research has confirmed that the presence of platforms is and California) or forked branches; deformities (e.g., broken considered the most important characteristic of murrelet tops); dwarf mistletoe infections; witches’ brooms; and nesting habitat (Burger 2002, Huff et al. 2006, McShane growth of moss or other structures large enough to provide a et al. 2004). Platform presence is more important than the platform for a nesting adult murrelet (Hamer and Cummins size of the nest tree because tree size alone may not be a 1991; Hamer and Nelson 1995; Singer et al. 1991, 1992). good indicator of the presence and abundance of platforms These nesting platforms (fig. 5-3) are generally (Evans Mack et al. 2003). Tree diameter and height can be located ≥33 ft (10 m) above ground (reviewed in Burger positively correlated with the size and abundance of plat- 2002 and McShane et al. 2004). These structures are forms, but the relationship may change depending on the variety of tree species and forest types that murrelets use for nesting (Burger et al. 2010, Huff et al. 2006, Raphael et al. 2011). Overall, nest trees in Washington, Oregon, and northern California have been greater than 19 inches Nick Hatch (48 cm) diameter at breast height (d.b.h.) and greater than 98 ft (30 m) tall (Hamer and Meekins 1999, Hamer and Nelson 1995, Nelson and Wilson 2002). Northwestern forests and trees typically require 200 to 250 years to attain the attributes necessary to support murrelet nesting, although characteristics of nesting habitat sometimes develop in younger western hemlock (Tsuga heterophylla) forests with dwarf mistletoe. Marbled murrelets are reported to nest dispropor- tionately on lower slopes and near streams. The recovery plan for the murrelet (USFWS 1997) states, “With respect to slope, eighty percent of nests in the Pacific Northwest were located on the lower one-third or middle one-third of the slope.” Hamer and Nelson (1995) showed the mean distance to streams from murrelet nests in the Pacific Northwest to be 159 m (509 ft). In southern California, Baker et al. (2006) found that murrelet nest sites were located closer to streams, and were located lower on slopes than random sites, based on analysis of variance models. Baker et al. (2006) found that nest sites were much closer to streams than would be expected based on randomly available sites within old-growth forests. Nest sites may have been located near streams because these Figure 5-3—Nesting platforms usually include large branches and sites afforded murrelets better access from at-sea flyways. other structures large enough to provide a platform for a nesting adult murrelet. 303 GENERAL TECHNICAL REPORT PNW-GTR-966 Other studies have also found proximity to streams or Guiding Questions other openings to be important for murrelet nesting in The mission statement for the Forest Ecosystem Manage- other regions as well (Hamer and Nelson 1995, Meyer ment Assessment Team (FEMAT) directed the team to take et al. 2004, Zharikov et al. 2006). In British Columbia, an ecosystem approach to forest management and particu- Rodway and Regehr (2002) found that forests bordering larly to address maintaining and restoring biodiversity on major stream channels provided high-quality nest habitat federal forests within the range of the northern spotted owl. for murrelets, with large trees, high epiphyte cover, and In addressing biological diversity, the team was directed many potential nest platforms. to develop alternatives that met, among other things, the Murrelets travel up to 55 mi (89 km) inland to reach objective of maintaining or restoring habitat conditions for suitable habitat in the northern part of their range in the the murrelet that would provide for viability of the species Pacific Northwest; inland distances narrow in the southern (FEMAT 1993: iv). Now, 22 years after the NWFP was portions of the range (table 5-1). Because murrelets depend initiated, national forests in the Plan area are preparing to on marine conditions for foraging and resting, and on revise their forest plans. Accordingly, U.S. Forest Service forests for nesting, both marine and forest conditions could managers have asked how the NWFP has been functioning limit murrelet numbers. Population declines attributed to to support the murrelet and what new science is relevant loss of mature and old-growth forest from harvesting, low to murrelet conservation and management.
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