Chapter 20 



Relationship of Marbled Murrelets with Habitat Characteristics 

 at Inland Sites in California 



Sherri L. Miller 



C. John Ralph 1 



Abstract: We examined the range and the relationships of Marbled 

 Murrelet (Brachyromphus marmoratus) behavior with habitat and 

 landscape characteristics in isolated old-growth and residual forest 

 stands from 2 to 400 ha in California. In large contiguous stands of 

 old-growth forest in parks, we examined relationships of murrelet 

 detections with elevation and topography. In isolated stands we 

 found higher murrelet detection levels in stands with higher domi- 

 nant and codominant crown cover and >50 percent coast redwood 

 (Sequoia sempervirens). Surveys also were more likely to detect 

 occupied behaviors at stands with higher crown cover and a greater 

 proportion of redwoods. Density of old-growth cover and species 

 composition may be the strongest predictors of murrelet presence 

 and occupancy in California. Contrary to previous studies, we did 

 not find that larger stands were more likely to have murrelets 

 present. In the large park stands, we found that mean detection 

 levels and the number of occupied stations were highest in the 

 major drainages and at lower elevations. Major ridges tended to 

 have lower detection levels and fewer occupied behavior stations. 



In recent years, much has been learned about the occurrence 

 of Marbled Murrelets (Brachyramphus marmoratus) at inland 

 forest sites. Throughout most of its range, the murrelet nests 

 in old-growth forests within 50-75 miles of the coast (Carter 

 and Morrison 1992). In California, Paton and Ralph (1990) 

 conducted general surveys (Paton, this volume) to determine 

 the distribution of murrelets in coastal old-growth and mature 

 second-growth forests. Concentrations were found in regions 

 containing large, contiguous, unharvested stands of old-growth 

 redwood, mostly within state and federal parks, with the 

 highest detection numbers in stands >250 ha. In excess of 

 200 detections for single-survey mornings have been recorded 

 at some survey stations in remaining unharvested stands 

 within parks in California, including Redwood National Park 

 and Prairie Creek State Park in Humboldt County (Ralph 

 and others 1990); and Big Basin State Park in San Mateo 

 County (Suddjian, pers. comm.). 



Federal listing of the Marbled Murrelet as threatened 

 (U.S. Fish and Wildlife Service 1992) has created a need for 

 information about the role of habitat and landscape features 

 for the murrelet. 



We conducted two studies to examine the relationships 

 of the murrelet to habitat and landscape characteristics within 

 old-growth forests, as defined by Franklin and others (1986). 

 In isolated stands in fragmented landscapes (the Stand Study), 

 we compared murrelet detections with stand size, structure, 



1 Wildlife Biologist and Research Wildlife Biologist, Pacific South- 

 west Research Station, USDA Forest Service, Redwood Sciences Labora- 

 tory, 1700 Bayview Drive. Arcata, CA 95521 



and landscape characteristics. In large contiguous stands of 

 old-growth in state and federal parks (the Park Study), we 

 examined murrelet detections with landscape features, such 

 as elevation and topography. We confined our study to old- 

 growth forests, because previous studies indicate murrelets 

 nest only in forests with these characteristics. 



Methods 



The survey methods followed the intensive survey 

 protocol of Ralph and others (1993). To maximize the number 

 of visual detections, we selected station positions at the 

 edges of the isolated stands or at interior locations with 

 openings in the canopy whenever possible. Observers could 

 move within a 50-m radius of the station. 



We estimate that, for an individual forest stand, four 

 surveys are needed to determine with a 95 percent probability 

 that murrelets are present (appendix A). If below canopy 

 behaviors were observed, we categorized the stand as 

 Occupied (see below) for analyses. During 1992 and 1993 

 for the Stand Study, we attempted to survey each isolated 

 stand at least four times between 15 April and 7 August. 

 Surveys at each stand were distributed throughout the survey 

 period whenever possible. However, due to difficult access 

 for some stands, surveys in some areas were temporally 

 aggregated. To eliminate potential effects from aggregated 

 surveys, detection levels were standardized for seasonal 

 variation (see Analyses below). 



For the 1993 Park Study, within the boundaries of the 

 large stands of old-growth forests in national and state parks 

 (fig. 1\ stations were placed in a matrix over the landscape, 

 as illustrated in figure 2. We surveyed all sections of park 

 stands with adequate accessibility. We placed stations 400 

 meters apart on roads and trails, and 400 meters out 

 perpendicular to trails, creating a matrix. Ralph and others 

 (1993) found that observers detect few birds at distances 

 >200 m, therefore, we assumed each station covered a 200- 

 m radius circle, approximately 12.5 ha. Due to safety 

 considerations for observers hiking to stations in pre-dawn 

 hours, we limited stations to within 400 meters of a trail or 

 road. Stations were surveyed once during the survey season. 

 We attempted to avoid surveys at adjacent stations on the 

 same morning. 



The species' range in northern California was determined 

 by examining the results of inland surveys conducted from 

 1988 through 1992 by government agencies and private 

 landowners. Murrelet use for each stand or station was 

 determined by the number and type of detections. All survey 

 stations were digitized into a Geographic Information System 



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



205 



