Burger 



Chapter 16 



Inland Habitat Associations in British Columbia 



Murrelets were also studied in subalpine forests in the 

 Caren Range, Sechelt Peninsula (Jones 1992). Dominant 

 trees were mountain hemlock and yellow cedar. This is very 

 old forest and one cedar stump was 1717 years old. Detection 

 frequencies from scattered stations in June and July in 1991, 

 1992 and 1993 averaged 13.9 13.8 (s.d.; n = 27; range 1- 

 61), 17.6 16.7 (17; 0-45), and 20.3 13.7 (54; 0-57), 

 respectively (P. Jones, pers. comm.). Vegetation was not 

 analyzed in detail. A nest was found here in a yellow cedar 

 in 1993 (Jones 1993). 



High densities of murrelet detections (mean 24.4 20.7 

 s.d.. range 9-85, n = 12) were obtained at Tsitika Creek 

 station between 29 June and 15 July 1991 in the lower Tsitika 

 Valley, northeastern Vancouver Island (MacDuffee and others 

 1993). A second station nearby, affording less visibility, 

 yielded only 1-4 detections in two surveys in this period. 

 Western hemlock (mean d.b.h. = 73 cm), western redcedar 

 (117 cm), amabilis fir (75 cm) and Sitka spruce (112 cm) 

 made up 60 percent, 18 percent, 16 percent and 7 percent, 

 respectively, of the trees with d.b.h. >7.5 cm in this stand. 



Vegetation analysis has been done in Carmanah-Walbran, 

 Vancouver Island in conjunction with murrelet surveys in 

 1990-1993 (Burger 1994, Manley 1992, Manley and others 

 1992). This is an area of relatively unfragmented valley- 

 bottom old-growth, dominated by western hemlock (47 percent 

 of all sampled stems >10 cm d.b.h.; 37.7 percent of combined 

 basal area), amabilis fir (41.8 percent; 19.2 percent), Sitka 

 spruce (8.4 percent; 33.3 percent), western red cedar (2.6 

 percent; 9.7 percent) with a few red alder. Six nests have 

 been found in this area, five in large Sitka spruce (d.b.h. 



range 1.33-3.7 m) and one in a large western hemlock 

 (d.b.h. 2.1 m). Manley (1992) found that murrelet detections 

 at six stations were positively correlated with combined 

 basal areas of hemlock and spruce, and negatively correlated 

 with combined fir and cedar. Burger (1994) used a larger 

 sample (11 stations in 1991, 12 in 1992) and considered a 

 wider range of habitat variables, including stem densities 

 and basal areas of all species, combinations of species, snags 

 and trees >1 m d.b.h.. He found the same patterns as Manley, 

 but the only significant correlation was a negative relationship 

 between detection rate and stem density of hemlock in 1991 

 (and not 1992). Burger (1994) concluded that the habitat 

 variables measured were too coarse, and detection rates too 

 variable, to detect subtle variations in suitability in this 

 relatively homogeneous watershed. All of the stations were 

 clearly in suitable nesting habitat, and occupied behaviors 

 had routinely been recorded at all stations (fig. 4). 



Manley and others (1994) sampled 14 sites in old- 

 growth forest in the Megin Valley, central Vancouver 

 Island. These were grouped into sites dominated by western 

 hemlock (4 sites), western red cedar (4), Sitka spruce (5) 

 and amabilis fir ( 1 ), although all sites supported a variety 

 of these large trees. Analysis of detection frequencies in 

 June and July 1993 showed that the spruce sites had 

 significantly lower detection rates than either cedar or 

 hemlock, but cedar and hemlock did not differ significantly 

 (table 1). The differences disappeared when only occupied 

 detections were considered, because spruce sites had higher 

 proportions of occupied detections (14 percent) than 

 hemlock (4 percent) and cedar (3 percent). Average tree 



Table 1 Mean (s.d.) detection frequencies of Marbled Murrelets in three forest types in the Megin Valley, central 

 Vancouver Islands in June and July 1993 (from Manley and others 1994) 



1 Multiple Kmskal- Wallace comparisons 



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



157 



