Hamer Chapter 17 Inland Habitat Associations in Western Washington 



Table 2 Sample size of stands used in the step-wise logistic regression analysis, listed by physiographic province and stand status. 



1 Stand status codes were: = Marbled Murrelets observed circling the stand; 1 = nest platform was located; 2 = juveniles, eggs, or eggshell fragments were 

 located; 3 = murrelets were observed flying in the canopy; 4 = murrelets were detected in the area; and 5 = no murrelets were detected. Occupied stands included 

 status codes 0-3 



Only dominant trees > 81 cm in diameter were included 

 in all vegetation measurements except for canopy closure and 

 forest vegetation series. In addition, only conifer trees were 

 included in the measurement for each variable, except canopy 

 closure. To ensure that a large sample of tree measurements 

 for each variable were recorded from each site, at least 20 

 trees were measured at each plot. If 20 trees were not available 

 within the plot, the nearest dominant trees to plot edge were 

 selected to be measured until 20 trees were recorded. Trees 

 selected outside the plot were included in the calculations for 

 mean tree d.b.h., total number of potential nest platforms, 

 potential nest platforms/tree, lichen coverage, dwarf mistletoe 

 (Arceuthobium spp.) infestation, moss (Isothecium spp.) 

 coverage on potential nest platforms, and all tree species 

 composition variables. Trees within the plot were used to 

 calculate basal area, forest zone, vegetation series, canopy 

 closure, mean canopy height, and all other measurements. 



Ecozones, geographical areas of roughly similar 

 environments, were delimited on the basis of the abundance 

 and distribution of plant indicator species and are a general 

 measure of the amount and kind of precipitation an area 

 received. Ecozones were mapped in Washington by the USDA 

 Forest Service (Henderson and others 1989, 1991). Ecozone 

 represented the wettest part of the study area (457 cm or 

 more of annual precipitation), whereas ecozone 13 was the 

 driest (less than 203 cm). Each plot was given an ecozone 

 classification based on its location. The vegetation series 

 and forest zone were identified for each plot using standard 

 protocol and field guides (Henderson and others 1989, 1991). 

 The latitude and distance to nearest salt water for each site 

 was measured using topographic maps with a scale of 

 1:250,000. Latitude was measured to the nearest minute and 

 distance to salt water to the nearest 0.4 km. 



The number of potential nest platforms (platform total) 

 for each tree was estimated from one point near the tree 



where the maximum number of limbs could be seen. The 

 observer counted the number of limbs or structures >15 m in 

 height and >18 cm in diameter directly along the tree bole. 

 All structures were counted; the observers did not make 

 judgments as to the suitability of the platforms for nesting. 

 These measurements were chosen because all of the 1 8 nests 

 found at the time the index was developed were >27 m in 

 height with the majority of nest limbs >20 cm in diameter. 

 Therefore, limbs >18 cm seemed a reasonable threshold to 

 use for the index. To practice estimating whether tree limbs 

 were >18 cm, limbs of known diameters were observed from 

 a 30-m distance. A total count of all potential nest platforms 

 in a tree was not possible, so this measurement was treated 

 as an index. Mistletoe blooms located away from the tree 

 bole were not counted as platforms, since their abundance 

 was measured using another index. Mistletoe infestation 

 was rated for each tree following an index developed by 

 Hawksworth (1977). The number of trees infected with 

 mistletoe (mistletoe number) were summed for each plot. 



The percent cover of all epiphytes (moss and lichens 

 separately) on the surface of the limbs of dominant trees was 

 recorded for each tree by estimating the average cover for all 

 limbs using five categories, including 0-20 percent, 21-40 

 percent, 41-60 percent, 61-80 percent, and 81-100 percent 

 cover. Each tree was placed in a category and an average 

 calculated for all trees in the plot for both lichen and moss 

 coverage. Moss cover (mean moss) was estimated for potential 

 nest platforms only. Lichen cover (mean lichen) on the 

 surface of the limbs of dominant trees was estimated by 

 averaging all the limbs of the tree. The average percent moss 

 coverage (percent moss) on all the limbs of dominant trees 

 in the plot were also estimated to the nearest 5 percent, as an 

 additional measure of moss abundance. 



Canopy closure was measured in a smaller 17.8-m plot 

 by physically measuring all gaps in the canopy >4 m 2 in size. 



166 



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



