Chapter 16 



Inland Habitat Associations of Marbled Murrelets in 

 British Columbia 



Alan E. Burger 1 



Abstract: Most Marbled Murrelets (Brochyromphus marmoratus) 

 in British Columbia nest in the Coastal Western Hemlock 

 biogeoclimatic zone. In this zone, detection frequencies were highest 

 in the moister ecosections and in low elevation forests. Nests and 

 moderately high levels of activity were also found in some forest 

 patches in the subalpine Mountain Hemlock zone. There was no 

 evidence of nesting in subalpine scrub forest, lowland bog forest, 

 or alpine tundra. Studies on the Queen Charlotte Islands and 

 Vancouver Island reported consistently higher detection frequen- 

 cies in old-growth than second growth forests (20-120 years old). 

 Detections in second-growth were usually associated with nearby 

 patches of old-growth. Within low elevation old-growth, detection 

 frequencies were sometimes positively correlated with mean tree 

 diameter, but showed weak or no associations with tree species 

 composition and minor variations in forest structure. Sitka spruce 

 (Picea shchensis ) and western hemlock (Tsuga heterophylla) were 

 important components of many high-activity sites. High murrelet 

 activities were associated with well-developed epiphytic mosses, 

 but mistletoe seemed less important. A study on Vancouver Island 

 showed higher predation of artificial nests and eggs at forest edges, 

 which suggests problems for Marbled Murrelets in fragmented 

 forests. The use of detection frequencies in the selection and 

 preservation of potential nesting habitat is discussed and the limi- 

 tations of single-year studies are exposed. 



British Columbia supports a significant portion of 

 the North American population of Marbled Murrelets 

 (Brachyramphus marmoratus). Over the past century, 

 evidence accumulated that the birds nested in large trees 

 in British Columbia (Campbell and others 1990), and at 

 least one early biologist made the connection between 

 declining numbers of murrelets and the reduction of old- 

 growth forests on eastern Vancouver Island (Pearse 1946). 

 In recent decades the pace of logging of coastal old- 

 growth forests has greatly increased. Between 1954 and 

 1990 about half of the large-tree old-growth forest on 

 Vancouver Island (75 percent in the southern island) was 

 logged (Husband and Frampton 1991). Out of 354 forested 

 watersheds larger than 5,000 ha in coastal British Columbia, 

 only 20 percent are pristine and 67 percent have been 

 significantly changed by industrial activity, primarily 

 logging (Moore 1991). Concerns over the effects of logging 

 on Marbled Murrelet populations were raised by Sealy 

 and Carter (1984), but there were no intensive inland 

 studies until the species was listed as threatened in Canada 

 in 1990. Loss of nesting habitat by logging was considered 



1 Associate Professor (Adjunct). Department of Biology , University of 

 Victoria, Victoria, British Columbia, V8W 2Y2, Canada 



the greatest threat (Rodway 1990, Rodway and others 

 1992). The listing stimulated several inland studies, 

 including reconnaissance surveys in many watersheds of 

 the Queen Charlotte Islands (Rodway and others 1991, 

 1993a) and Vancouver Island (Savard and Lemon in press) 

 and intensive surveys at several sites. 



Identification and mapping of potential nesting habitats 

 was identified as a high priority for research in the National 

 Recovery Plan for the Marbled Murrelet, prepared by the 

 Canadian Marbled Murrelet Recovery Team (Kaiser and 

 others 1994). Detailed 1:50,000 maps of coastal old-growth 

 forests are being prepared (Derocher, pers. comm.). There 

 are still very few data available for either landscape- or 

 stand-level analyses of habitat associations. I review the 

 available data and point out research topics that urgently 

 need to be addressed. 



Methods and Sources of Data 



The studies reviewed here followed the Pacific Seabird 

 Group survey protocols for general (road) and intensive 

 (fixed station) surveys (Paton and others 1990, Ralph and 

 others 1994), with the exception of Eisenhawer and Reimchen 

 (1990) and Reimchen (1991). 



Rodway and others (1991; 1993a,b) did intensive 

 sampling through the 1990 season in Lagins Creek and 

 Phantom Creek on Graham Island, and less frequent general 

 surveys in 1 2 other watersheds on the Queen Charlotte Islands. 

 Savard and Lemon (in press) analyzed data from 382 surveys 

 at 151 fixed stations and 88 road surveys in 82 watersheds 

 on Vancouver Island in 1991. Relatively few surveys were 

 made at each station (mean 1.6, range 1-5). and large numbers 

 of observers were used with variable degrees of training. 

 Savard and Lemon (in press) warned that their data could 

 not present an accurate picture of murrelet activity in any of 

 the watersheds surveyed. Nevertheless, some significant 

 patterns emerge at the landscape scale. 



The remaining studies focussed on fine-scale temporal 

 and spatial variations within single watersheds during one 

 season (Eisenhawer and Reimchen 1990; MacDuffie and 

 others 1993; Manley and others 1992, 1994) or 3-4 seasons 

 (Burger 1994; Jones 1992, 1993). Only three studies combined 

 repeated intensive surveys with detailed habitat analysis at a 

 variety of sites (Burger 1994, Manley and others 1994, 

 Rodway and others 1993a). These data are insufficient for a 

 thorough examination of habitat patterns at stand and 

 landscape scales in British Columbia, but some trends are 

 apparent and are reviewed here. Figure 1 shows the location 

 of the study sites. 



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



151 



