Hamer and Nelson 



Chapter 6 



Characteristics of Nest Trees and Nesting Stands 



The sample size for each nest characteristic varied because 

 some variables were not measured at some nest sites, or the 

 information was not available to us. A protocol that outlined 

 a methodology for measuring the structure of nests was not 

 available until 1993 (Hamer 1993), so some characteristics 

 of earlier nests were not measured. Stands were delineated 

 and stand sizes calculated generally by defining stands as a 

 contiguous group of trees with no gaps larger than 100 m. 

 Stand ages were derived from stand information data bases 

 of the landowners or by aging individual trees in the stand 

 using increment bores. Limb diameters were generally 

 reported with the moss cover on the limb included in the 

 measurement. Nest platform lengths were measured as the 

 length of the nest branch until it was judged to be too narrow 

 to support a nest (<10 cm). 



We calculated the range, mean, and standard deviation 

 for each nest and stand characteristic for each state or province. 

 In addition, we pooled the sample of nests for what we term 

 the "Pacific Northwest", using data from nests located in 

 California, Oregon, Washington, and British Columbia (tables 

 2 and 3). Nests located in Alaska were treated as a separate 

 sample (tables 2 and 3). 



We chose to segregate the data using state or provincial 

 boundaries because different forest types generally occur 

 within these boundaries. Forest types in California within the 

 murrelet's breeding range were predominately coastal redwood 

 (Sequoia sempervirens). Oregon had fire regenerated stands 

 dominated by Douglas-fir (Pseudotsuga menziesii), and in 

 Washington, mixed forests of western red cedar (Thuja plicata), 

 western hemlock, Douglas-fir, and Sitka spruce (Picea 

 sitchensis), created by the combined forces of fire and wind, 

 covered the majority of the landscape. British Columbia was 

 similar to Washington, with the addition of yellow cedar 

 (Chamaecyparis nootkatensis), found in stands at higher 

 elevations. Forest types in Alaska were very distinct, with 

 many stands dominated by mountain hemlock (Tsuga 

 mertensiand) which were small in stature and diameter. 



Results 



Landscape Characteristics 



Distance to Salt Water 



A sample of 45 nests in the Pacific Northwest were 

 located a mean distance of 16.8 km inland (table 2, fig. 1). 

 Nests in California were found a mean distance of 13 km 

 from salt water; the farthest inland nest in California was 

 located 28.9 km inland (table 2). The farthest inland nest in 

 Oregon was located 40 km from the sea. This coincides with 

 a historical record of a downy young found on the ground 40 

 km inland on the South Fork of the Coos River in Coos 

 County (Nelson and others 1992). In Washington, nests 

 were located a mean distance of 16 km inland. Other 

 information from Washington indicated nesting at stands 

 further inland than known nest sites. A small downy chick 

 was located by the senior author on the ground along a trail 

 on the east shore of Baker Lake in 1991, 63 km from the 

 ocean. Another downy chick was located 45 km inland in 



Helena Creek, in Snohomish County (Reed and Wood 1991). 

 Six additional records of eggs, downy young, and fledglings 

 found 29-55 km inland in Washington were compiled by 

 Leschner and Cummins ( 1 992a), and Carter and Sealy ( 1 987b). 

 In British Columbia, nest trees were located a mean 

 distance of 1 1.5 km from the Pacific. In addition, there was a 

 record of a fledgling found on the ground near Hope, British 

 Columbia, 101 km from salt water (Rodway and others 

 1991). This is the farthest inland distance recorded for Marbled 

 Murrelets in North America. Nest trees in Alaska were 

 typically located close to the coast, with a mean distance of 

 0.5 km (table 2), corresponding to the closer inland distribution 

 of suitable nesting habitat. 



Elevation 



The mean elevation of nest trees from a sample of 45 

 murrelet nests in the Pacific Northwest was 332 m (table 2). 

 In Alaska nest trees were low in elevation with a mean of 96 

 m and a maximum of 260 m (table 2). 



Aspect 



Nest stands in the Pacific Northwest occur on a variety 

 of aspects. Twenty-six percent of the stands had northeast 

 aspects, 12 percent southeast, 28 percent southwest, 12 percent 

 northwest, and 21 percent were on flat topography with no 

 aspect (table 2). In Alaska, 93 percent of the nest stands had 

 westerly aspects (NW, W, or SW), with the majority (50 

 percent) facing northwest. 



Slope 



Nests in the Pacific Northwest were located on slopes 

 with moderate gradients, with a mean of 23 percent. Slope 

 gradients for nests in Alaska were higher than nests for the 

 Pacific Northwest with a mean slope of 69 percent. 



The majority of nests in the Pacific Northwest (80 percent) 

 were located on the lower one-third or middle one-third of 

 the slope. Nest stands in Alaska were located low in elevation, 

 but were usually located on the top one-third of the slope, 

 unlike nests in the southern part of the range. Nest stands in 

 Alaska have been described as being located on gradual or 

 moderate slopes (Naslund and others, in press). 



Forest Characteristics 



Age 



For a sample of 16 nests in the Pacific Northwest the 

 mean stand age was 522 years with the youngest stand age 

 reported as 180 years old (table 2). The oldest stand was 1,824 

 years old located on the mainland coast of British Columbia, 

 and was dated using nearby stumps from a recent clear-cut. To 

 date, all 61 tree nests found in North America have been found 

 in stands described as old-growth or mature forests. 



Tree Size 



The mean d.b.h. of trees in nest stands was not reported 

 for many sites. Nest stands in Washington and Oregon were 

 characterized by large diameter trees ( x = 47.7 cm), a mean 

 density of large trees (>46 cm d.b.h.) of 93.8/ha, an average 



72 



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



