Chapter 19 



Marbled Murrelet Habitat Associations in Oregon 



Jeffrey J. Grenier 1 - 2 



S. Kim Nelson 1 



Abstract: We described habitat associations of Maibled Murrelet 

 (Brachyramphus marmoratus) nesting (n = 10) and occupied 

 (n = 184) sites in Oregon. We compared habitat characteristics of 

 177 occupied sites to a random sample of 9,625 sites (n = 531) of 

 unknown murrelet status. In addition, we briefly described the char- 

 acteristics of 22 nests and compared 10 of the nest sites to adjacent 

 sites. In general, occupied sites were older, had larger midstory 

 trees, and had larger and greater densities of dominant 

 i or remnant) trees than random sites. In addition, dominant tree 

 height and density, midstory and understory tree diameter and per- 

 cent cover, and percent canopy closure were important habitat 

 components for predicting murrelet occupancy. All nests were in 

 old-growth Douglas-fir (Pseudotsuga menzfesii), western hemlock 

 ( Tsuga htterophylla ). and Sitka spruce (Picea sitchensis) trees > 1 27 

 cm in diameter and > 36 m tall. Murrelet nest sites had fewer trees/ha 

 and less canopy closure compaxd to adjacent sites. Our results 

 support previous studies that concluded murrelets use stands with 

 old-growth characteristics and that stand structure is more important 

 than stand age. Knowledge of habitat associations does not imply 

 habitat quality, which should be quantified through studies on repro- 

 ductive success in relation to habitat and landscape characteristics. 



Marbled Murrelets (Brachyramphus marmoratus) use 

 old-growth and mature forests, or forests with old growth 

 components, nearly year-round (Naslund 1993b, Nelson 

 1990b. Paton and Ralph 1990, Rodway and others 1991). 

 Characteristics of these forests have been analyzed at the 

 stand, landscape, nest, and nest-site levels (Burger, this volume 

 a: Hamer. this volume: Hamer and Nelson, this volume b; 

 Naslund and others, in press; Nelson and Hamer 1992; Rodway 

 and others 1991; Singer and others 1991, in press). From 

 these studies we know that murrelets nest in large diameter 

 trees and may be selecting stands based on number of potential 

 nest platforms, and density and diameter of dominant trees. 



Data on the distribution and habitat associations of 

 Marbled Murrelets have been collected in Oregon since 

 1988. This paper provides a synthesis of murrelet habitat 

 associations by using existing data on occupied stands and 

 nest sites, and summarizes new stand-level habitat data from 

 state and federal agencies. Our objectives were to: (1) 

 summarize habitat characteristics of occupied sites, (2) 

 determine habitat associations by comparing occupied sites 

 to other sites, and (3) identify the key habitat components of 

 murrelet habitat. Knowledge of Marbled Murrelet habitat 

 associations may assist in designing and implementing 

 successful habitat management plans for this species. 



1 Research Wildlife Biologists. Oregon Cooperative Wildlife Research 

 Unit. Oregon State University, Nash 104. Corvallis, OR 97331-3803 



2 Present address: 1402 Cedar Street, Philomath. OR 97370 



Study area 



Study sites were located in the Coast Range and Klamath 

 Mountain (Siskiyou Mountains) Provinces in Oregon (Franklin 

 and Dyrness 1973). These areas consisted of rugged, 

 mountainous terrain, with steep slopes and deeply cut river 

 and creek drainages. Elevations ranged from 50 m along the 

 coast of Oregon, to more than 1 200 m in the central mountains. 

 The climate consists of cool, wet winters and warm, dry 

 summers. Mean temperatures range from C in winter to 

 24 C in summer, and annual precipitation varies from ISO 

 to 300 cm (Franklin and Dymess 1973). 



These areas are primarily forested, although they have 

 been intensively managed for timber since the early 1900s, 

 and many stands are <200 years old. In addition, natural and 

 man-caused fires have altered many stands. Relatively small, 

 isolated patches of mature and old-growth tree species remain. 

 Douglas-fir (Pseudotsuga menziesii) was the dominant tree 

 species in the north and mixed-evergreen species, including 

 Douglas-fir and tanoak (Uthocarpus densiflorus), were 

 dominant in the south. 



Methods 



Between 1990 and 1993, murrelets were surveyed on 

 state and federal lands throughout the Coast Range and 

 Siskiyou Mountains, primarily within 50 km of the coast. 

 Surveys included intensive research surveys, and intensive 

 and general surveys for agency monitoring projects. Forest 

 stands were surveyed to existing protocols (Paton and others 

 1990, Ralph and Nelson 1992, Ralph and others 1993) and 

 were classified as occupied (birds exhibiting nesting or 

 below canopy activity), with murrelets present (presence), 

 or without murrelets (undetected), based on murrelet behavior 

 patterns. In addition, we searched for nests using three 

 methods: watching murrelets land in trees, searching for 

 eggshells on the forest floor, and climbing trees to examine 

 branches for nest cups. 



Characteristics of Occupied Sites 



Four databases were examined. The characteristics of 

 occupied sites were summarized using one state lands database 

 from Oregon Department of Forestry (Reagan, pers. comm.), 

 two U.S. Forest Service databases from the Siuslaw National 

 Forest (McCain, pers. comm.; Wettstein, pers. comm.), and 

 one research database from Oregon State University. Habitat 

 variables differed among databases. Similar habitat variables 

 were used in the analyses where possible. We used Spies 

 and Franklin's (1991) definition for stand age (i.e., young 

 stands = 40-80 years, mature = 80-200 years, and old- 

 growth = 200+ years). Remnant trees were defined as those 



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



191 



