Hamer and Nelson 



Chapter6 



Characteristics of Nest Trees and Nesting Stands 



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15 20 25 30 35 40 45 



DISTANCE FROM COAST (km) 



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Figure 1 Distances from the Marbled Murrelet nest trees (n = 35) to 

 the nearest salt water for nests found in the Pacific Northwest. The 

 number of nests was listed in 5-km increments beginning with nests 

 found 0-5 km inland. 



total tree density (>10 cm d.b.h.) of 324/ha, multiple canopy 

 layers (2-3), and the presence of snags (>10 cm d.b.h.) 

 (mean density = 71/ha) (Nelson and others, in press). In 

 Alaska, most nest trees were located in forests with 

 significantly larger tree size classes (>23 cm d.b.h.) and 

 higher volume classes (1883-5649 m 3 /ha) than other forest 

 types (Kuletz and others, in press). 



Tree Species Composition and Stem Density 



Conifer species that typically grow at higher elevations 

 in the Pacific Northwest include mountain hemlock, silver 

 fir (Abies amabilis), and yellow cedar. Conifer species 

 most abundant at lower elevations include Douglas-fir, 

 western red cedar, Sitka spruce, western hemlock, and 

 coastal redwood. Nest stands in the Pacific Northwest were 

 composed primarily of low elevation conifer species ( x = 

 91 percent) (table 2). In Alaska, the composition of low 

 elevation trees was much lower, with a mean of 64 percent. 

 The total mean tree density for nest stands in the Pacific 

 Northwest was 182 trees/ha; total density was about three 

 times greater in Alaska (table 2). 



All nest trees in the Pacific Northwest were recorded in 

 stands characterized as old-growth and mature forest. These 

 stands were dominated by either Douglas-fir, coast redwood, 

 western hemlock, western red cedar, or Sitka spruce. The 

 one exception was a higher elevation nest stand found in the 

 Caren Range of British Columbia which was dominated by 

 old-growth mountain hemlock (60 percent) with smaller 

 percentages of yellow cedar (20 percent) and silver fir (20 

 percent). In California, nest stands were dominated by coast 

 redwood and Douglas-fir, with a component of western 

 hemlock and Sitka spruce in some nest stands. In both 

 central and northern California, all nest sites had a higher 

 percentage of redwood trees than Douglas-fir. Nest stands 



in Oregon were dominated by Douglas-fir and western 

 hemlock, with one site dominated by Sitka spruce. Forest 

 types in Washington included stands dominated by western 

 hemlock, Douglas-fir, and Sitka spruce. These stands 

 commonly had a large component of western red cedar. 

 Silver fir made up a smaller component of some of the nest 

 stands in Washington. 



In British Columbia, six nest stands were dominated 

 primarily by Sitka spruce and western hemlock, with four 

 stands also having a component of silver fir, and one stand 

 with western red cedar. One nest stand in the Caren Range 

 was dominated by mountain hemlock. For a sample of eight 

 nests located in Alaska, mountain hemlock was the dominant 

 tree species at five nests, and western hemlock was the 

 dominant species at three nest stands (Naslund and others, in 

 press). Sitka spruce were reported as an important component 

 at most of these nest sites. 



Canopy Characteristics 



Nest stands in the Pacific Northwest had a mean canopy 

 height of 64 m with the redwood zone included in this sample 

 (table 2). The mean canopy height for stands located in Oregon, 

 Washington, and British Columbia was 61 m. The canopy 

 height of Alaska nest stands were lower ( x = 23 m), reflecting 

 the small stature of the trees in this geographic area. 



For nest stands in the Pacific Northwest, the mean canopy 

 closure was 49 percent, and all nest stands were reported to 

 have 2-4 tree canopy layers where this variable was recorded 

 (table 2). Canopy closures below 40 percent were reported 

 for 40 percent of the nest stands (fig. 2). Mean canopy 

 closures were especially low in California and Oregon. Canopy 

 closures for a typical old-growth stand in Washington 

 generally average 80 percent. Canopy closures reported from 

 Alaska were similar to nest stands in the Pacific Northwest 

 (table 2) with a mean of 62 percent. 



The presence of dwarf mistletoe (Arceuthobium) in the 

 nest stands or within the canopy of nest trees was not reported 

 consistently enough to determine its importance to murrelets. 

 Mistletoe was reported at 13 of 20 nest stands, where its 

 occurrence was evaluated. 



Stand Size 



Mean nest stand size for the Pacific Northwest was 206 

 ha. Several nest stands were only 3, 5, and 15 ha in size. In 

 Alaska, stands were naturally fragmented in many cases, 

 and averaged 3 1 ha. Stand sizes were generally smaller in 

 Alaska because of the naturally fragmented nature of the 

 coastal forests in this region. 



Distance to Openings 



Distance of nest trees to streams for nests in the Pacific 

 Northwest was variable, with a mean of 159 m. Nest trees 

 were located a mean distance of 92 m from natural or man- 

 made openings (table 2). A combined analysis indicated that 

 the mean distance to an opening or stream was 123 m (n = 

 68, s.d. = 177). Sixty-six percent of the nest trees were <100 

 m from an opening (fig. 3). 



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



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