Chapter 17 



Inland Habitat Associations of Marbled Murrelets in 

 Western Washington 



Thomas E. Hamer 1 



Abstract: Little research has been done to quantify and describe 

 the structural characteristics of forest stands that are associated 

 with Marbled Murrelet (Brochyromphus marmoratus) nesting in 

 the Pacific Northwest. Vegetation measurements and murrelet 

 surveys to determine occupancy were conducted in stands located 

 throughout western Washington. I used logistic regression to con- 

 trast stand attributes between occupied (n = 64) and unoccupied (n 

 = 87) stands. The probability of occupancy of an old-growth stand 

 increased with increasing total number of potential nest platforms, 

 percent moss coverage on the limbs of dominant trees (>81 cm 

 d.b.h.). percent slope, the stem density of dominant trees, and the 

 mean d.b.h. of western hemlock. The probability of occupancy of 

 a stand decreased as lichen coverage on the limbs of dominant 

 trees, stand elevation, and canopy closure increased. Mean detec- 

 tion rates and the percent of stands surveyed and verified as 

 occupied declined sharply with an increase in elevation over 1,067 

 m. and for stands >63 km from salt water. The relationship of the 

 number of potential nest platforms and elevation to the probability 

 of occupancy was best explained by comparing the structural 

 characteristics of old-growth trees for the five conifer species 

 available for nesting. Land management activities that reduce or 

 affect the number of potential nest platforms/ha, composition of 

 low elevation conifers, moss cover on tree limbs, stem density of 

 dominant trees (>81 cm d.b.h.), or canopy closure, would reduce 

 the quality of a site as nesting habitat for murrelets. Reproductive 

 success should be used as a measure of habitat suitability in future 

 studies by intensively studying occupied stands that have high 

 detection rates of Marbled Murrelets and locating a sample of 

 active nests to observe. 



The research attempts to quantify and describe the 

 structural characteristics associated with Marbled Murrelet 

 (Brachyramphus marmoratus) nesting habitat have examined 

 the general relationship between murrelet abundance and 

 stand age, stand size, and tree size. A more specific model 

 describing habitat is needed for a variety of reasons. A 

 model would help ( 1 ) assess the relative impacts that forest 

 management practices and associated activities will have on 

 the quality of murrelet nesting habitat, (2) evaluate the relative 

 suitability of a forest stand as nesting habitat for murrelets, 

 (3) more accurately map suitable habitat, (4) understand 

 how to speed the development of suitable habitat to meet 

 long-term objectives for maintaining or increasing murrelet 

 populations, (5) attempt to fashion habitat enhancement 

 techniques or mitigation measures, and (6) plan future habitat 

 research studies. 



1 Research Biologist, Hamcr Environmental. 2001 Highway 9, ML 

 Veroon. WA 98273 



Studies specifically addressing the forest habitat 

 associations of Marbled Murrelets in Washington were 

 initiated in 1990 and continued through 1993. A 1990 study 

 examined the association of murrelets to four broad habitat 

 categories and recorded the distribution and abundance of 

 murrelets within an entire drainage basin, beginning at the 

 Cascade crest and ending at its terminus with the Puget 

 Sound (Hamer and Cummins 1990). An analysis of murrelet 

 detection rates relative to the percent of old-growth forest 

 available on the landscape was also conducted in this study. 

 Studies from 1991 to 1993 focused on describing and 

 analyzing the structural differences between old-growth stands 

 occupied by murrelets and unoccupied old-growth stands. 

 The results of these structural analysis are presented in this 

 paper. In addition, a landscape analysis examining the 

 attributes associated with stands occupied by Marbled 

 Murrelets was completed in Washington in 1994 (Raphael 

 and others, this volume). 



Methods 



Landscape Characteristics 



Detection Rate Comparisons 



For the comparison of Marbled Murrelet detection 

 (murrelet detections/survey morning) and occupancy rates 

 (number of stands surveyed and verified as occupied/number 

 of stands surveyed) with respect to elevation, inland distance, 

 and physiographic province, 262 old-growth stands were 

 used. To investigate the effect of elevation on murrelet 

 detection and occupancy rates, the mean detection rate and 

 the percent of old-growth stands found occupied by murrelets 

 were averaged for each 150-m interval in elevation ranging 

 from to 1 ,500 m. To determine the effect of inland distance 

 on habitat use by murrelets, the mean detection rate and 

 percent of old-growth stands verified as occupied were 

 averaged for inland distances using 15 -km intervals ranging 

 from to 95 km. The mean detection rate and the percent of 

 stands surveyed and verified as occupied were also used as 

 measures of the use of a region by murrelets. The 

 physiographic provinces we used for data comparisons are 

 those described by Franklin and Dyrness (1973). Of the 262 

 old-growth stands in this analysis, 132 stands occurred in the 

 North Cascades Province, 32 in the South Cascades, 80 on 

 the Olympic Peninsula, 8 in the Coast Range (southwest 

 Washington), and 10 stands in the Puget Trough Province. 



Inland surveys for Marbled Murrelets were conducted 

 using standardized survey techniques developed by the Pacific 

 Seabird Group Marbled Murrelet Technical Committee (Ralph 



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



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