Hamer and Nelson 



Chapter 6 



Characteristics of Nest Trees and Nesting Stands 



10 20 30 40 50 60 70 80 90 100 

 CANOPY CLOSURE OF STAND AROUND NEST(%) 



Figure 2 Canopy closure of the stand surrounding the nest tree for 34 

 Marbled Murrelet nests found in North America. The number of nests 

 was listed in 10-percent increments beginning with nests with 0-10 

 percent canopy closure. 



150 250 350 450 



DISTANCE FROM STREAM OR OPENING (m) 



500 



Figures Distances from the Marbled Murrelet nest trees (n = 68) to the 

 nearest stream, creek, or opening for nests found in North America. 

 Some nests had two measurements, one to the nearest opening and 

 one to the nearest stream. 



Tree Characteristics 



Nest trees used by murrelets in the Pacific Northwest 

 included Douglas-fir (57 percent), Sitka spruce (15 percent), 

 western hemlock (13 percent), coast redwood (1 1 percent), 

 and western red cedar (2 percent) (table 3). In one exception, 

 a nest in British Columbia was found in a yellow cedar (2 

 percent). Western hemlock was the only nest tree species 

 reported used by Marbled Murrelets throughout their 

 geographic range. Although Sitka spruce was only reported 

 from Alaska, British Columbia, and Oregon, it is likely this 



species is also used throughout the range of the murrelet 

 since it is common in coastal coniferous forests of Washington 

 through California. Douglas-fir nest trees were only located 

 in Washington, Oregon, and California. Nests in cedar trees 

 were reported only from Washington and British Columbia, 

 but this was probably due to a small sample size. Mountain 

 hemlock nest trees were only reported from Alaska. 



In the Pacific Northwest, the mean nest tree diameter 

 was 211 cm, with the smallest diameter nest tree reported 

 from Washington, which was a western hemlock 88 cm in 

 diameter (table 3). Nest tree diameters were normally 

 distributed with a maximum number of trees found between 

 140 and 160 cm, and 85 percent of the trees ranging between 

 120 and 280 cm (fig. 4). Nest tree diameters were much 

 smaller in Alaska ( x = 63 cm) due to the small stature of the 

 trees in this region. 



Mean nest tree heights were highest in California and 

 Oregon where the majority of nest trees were in redwood 

 and Douglas-fir trees which can grow to great heights. Mean 

 tree heights were similar between Washington and British 

 Columbia where more of the nest trees were in cedar, spruce, 

 and hemlock. Mean tree heights in the Pacific Northwest 

 were 66 m (table 3). Nest tree heights in Alaska were low, 

 with a mean of 23 m, with one nest tree measured at 16m. 



The mean diameter of the tree trunk at nest height was 

 88 cm in the Pacific Northwest, with minimum trunk diameters 

 of 36 cm and 40 cm reported for Oregon and Washington 

 respectively. Trunk diameters at the nest height were not 

 reported for nests in Alaska (table 3). 



The condition of nest trees in the Pacific Northwest 

 varied, with 64 percent recorded as alive/healthy and 36 

 percent as declining (n = 44). No nests were reported in 

 snags. Nest trees with declining tops (8 percent), broken 

 tops (37 percent) and dead tops (8 percent) were commonly 

 reported, with only 47 percent of the nest tree tops recorded 

 as alive/healthy. In Alaska (n = 14), 57 percent of the nest 

 trees were reported as declining, and one nest tree was 

 recorded as dead. 



In the Pacific Northwest, mean nest branch height was 

 45 m (table 3). Mean nest branch height was highest in 

 California and Oregon, where the mean tree height was also 

 the highest. Mean nest branch height was lowest in Alaska 

 (13 m), with one nest located only 10 m above the ground. 



The mean diameter of nest branches measured at the 

 tree trunk and at the nest varied little between each state or 

 Province for the Pacific Northwest (table 3). Mean nest 

 branch diameters at the nest for each state or province ranged 

 from 27-34 cm with a mean diameter of 32 cm for the Pacific 

 Northwest. The distribution of limb diameters at the nest in 

 the Pacific Northwest were normally distributed, with a 

 maximum number (22 percent) of nests located on limbs 35- 

 40 cm in diameter (fig. 5). In Alaska, the smallest branch 

 diameters at the nest were 12, 14, and 16 cm, with a mean 

 diameter of only 19 cm. The length of the nest branches in 

 the Pacific Northwest ranged from 1 m to 14 m, with a mean 

 length of 5.3 m (n = 42). 



76 



USD A Forest Service Gen. Tech. Rep. PS W- 152. 1995. 



