Grenier and Nelson 



Chapter 19 



Inland Habitat Associations in Oregon 



Table6 Comparison' of vegetationcharacteristicsbetween25-meterplotsaroundnesttreesandwithinthreeplots 2 

 adjacent to 10 nest trees found in Oregon between 1990 and 1992 



Nest platforms (no./tree) 



Mistletoe abundance 



Snag density (no./ha) 



Snag height (m) 



Snag d.b.h. (cm) 

 Snag decay class 



2.2 



5.4 



(0.4) 



0.0-4.0 



(0.9) 

 2.0-11.0 



7.5 



(2.0) 

 2.0-21.2 



75.4 



3.7 



(9.0) 

 30.8-108.3 



(0.2) 

 1-5 



2.3 



(0.5) 

 1.0-5.0 



(1.7) 

 1.3-18.7 



15.5 



(2.1) 

 4.9-24.8 



81.4 



3.3 



(7.4) 

 33.2-113.0 



(0.1) 

 1-5 



0.61 



0.29 



0.03 



<0.001 



1 Comparisons based upon a Wilcoxon paired-sample test for all characteristics except decay class of snags which 

 is compared using a Chi-square test and a Bonferroni Z-statistic (Neu and others 1974) for the distribution of 

 observations within five decay-class categories. 



2 Characteristics measured within two adjacent plots at one nest site. 



been in older-aged forests, with high densities of dominant 

 trees (Burger, this volume a; Hamer, this volume; Miller 

 and Ralph, this volume; Nelson 1989, 1990a; Paton and 

 Ralph 1990). In addition, in British Columbia, the presence 

 of murrelets was correlated with the presence of Sitka spruce 

 and western hemlock, low elevations, and large trees which 

 had platforms for nesting (Burger 1994, this volume a; 

 Manley and others 1992; Rod way and others 1991). In 

 Washington, number of platforms and moss abundance were 

 the most important variables for predicting murrelet 

 occupancy (Hamer, this volume). Elevation (low) and canopy 

 closure (moderate) were also key characteristics of occupied 

 sites (Hamer, this volume). 



Nest Sites 



Murrelets used mature or old-growth forests and large 

 diameter Douglas-fir, Sitka spruce, and western hemlock trees 



for nesting. Nests (n = 22) were on large limbs ( x = 29 A cm) 

 usually 1 8 m or more above ground level, and were located 

 in trees > 127 cm ( x= 187.9) in diameter. Other structures at 

 the nest were also important, including high vertical canopy 

 cover above the nest cup (x = 78.9 percent). In addition, all 

 nests were located in forests with multi-layered canopies (2- 

 3) with a wide range of both tree densities (121.0-718.8 ha) 

 and canopy cover (12-99 percent). 



In general, the forest immediately around the nest trees 

 was open, with fewer dominant trees. The density of 

 dominant trees at nest sites was lower than at adjacent sites. 

 However, occupied sites had a higher density of dominant 

 trees than random sites. Apparently, it is important for 

 murrelets to have numerous dominant trees throughout a 

 stand to provide nesting opportunities, but at the nest site, 

 a lower density of dominant trees may facilitate access to 

 the nest tree for a bird with limited flying maneuverability. 



200 



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

 i 



