Grenier and Nelson 



Chapter 19 



Inland Habitat Associations in Oregon 



Table 5 Summary of nest and nest tree characteristics from 22 nests found in Oregon between 1990 and 1993 



I 



Distance from trunk to 



Nest cup 

 Length (cm) 

 Width (cm) 

 Depth of cup (cm) 

 Depth of moss on branch (cm) 



Nest platform 

 Length (cm) 

 Width (cm) 

 Canopy closure above nest (pet.) 



12.0 



11.1 



3.1 



5.2 



1.0 

 0.7 

 0.3 

 0.6 



6.0-26.0 

 7.0-17.8 

 0.5-5.1 

 0.6-12.0 



19 

 19 

 17 

 18 



1 Characteristics were not measured at some nests. 



2 Excludes a nest in a Sitka spruce 7.6 m from the trunk. This nest was 3.3 times farther than the next most distant 

 nest and 1 1 .2 times farther than the mean. 



Tree species composition of occupied sites was consistent 

 with composition across the landscape. The western hemlock/ 

 Oregon oxalis plant association, within the western hemlock 

 zone, was especially important. These sites are very fertile 

 and moist and may produce larger trees (Hemstrom and 

 Logan 1986). In addition, moisture in these sites may decrease 

 the likelihood of intense fires, thereby allowing higher 

 densities of remnant trees. 



Historically, extensive, and sometimes catastrophic, fires 

 occurred in the Oregon Coast Range (Agee 1994). These 

 fires created diverse forests with attributes of older-aged 

 forests that are not found in intensively managed plantations. 

 For example, natural stands generally have more tree species, 

 less uniform tree sizes, more random spacing of trees, and 

 larger remnant overstory trees, as compared to even-aged 

 stands of the same age (Spies and Franklin 1991). Many of 

 the occupied sites in Oregon were created naturally, and 

 many have not been managed (i.e., thinned or partially 

 harvested). Thus, these sites were uneven-aged forests and 

 they included a variety of tree sizes and ages. Spacing of the 

 dominant trees was not uniform, allowing midstory and 

 understory trees to fill in the gaps in the canopy. The structure 

 of these forests, in most cases, was similar to old-growth 



forests, although tree density was lower and average tree 

 size smaller than "classic" old-growth (as defined in Franklin 

 and others 1986). It is the structure of these stands, the large 

 trees with nesting platforms, hiding cover (vertical canopy 

 cover), and variable canopy cover, that are important to 

 murrelets. Mean tree age alone and low canopy closure do 

 not indicate the quality of the habitat. For example, some 

 sites on state lands were typed as young (<80 years old), yet 

 all of these sites had remnant trees (>66 cm d.b.h.), except 

 one, and all had other older forest structures that survived or 

 were created by fire (snags, woody debris). The single young 

 site without remnant trees was located adjacent to and 

 contiguous with a stand that contained 42.0 remnant trees per 

 ha. In addition, while low canopy closure may allow murrelets 

 access to nests, most (70 percent) nests near openings or 

 edges have been unsuccessful (Nelson and Hamer, this volume 

 b). Therefore, suitable murrelet habitat likely includes complex 

 structure, high densities of large trees, large nesting platforms, 

 and hiding cover. 



The key components of occupied sites in this study 

 were similar to occupied sites throughout the Pacific 

 Northwest and California, and to other studies in Oregon 

 (Nelson 1989, 1990a). Most sites used by murrelets have 



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



199 



