O'Donnell and others 



Chapter 1 1 



Patterns of Seasonal Variation of Activity 



Figure 5 Weekly mean (s.e.) numbers of Marbled Murrelet detections per survey at 

 Phantom Creek, British Columbia, in 1990. A total of 49 morning surveys were 

 conducted. From Rodway and others 1993b. 



Figure 6 Weekly mean (s.e.) numbers of Marbled Murrelet detections per 

 survey at Lagins Creek, British Columbia, in 1 990. A total of 33 morning survey 

 were conducted. From Rodway and others 1993b. 



late May, similar to that reported by Nelson (1989). At two 

 sites, detection levels during this period were approximately 

 equal to or even exceeded those during July. 



Patterns of Detections in Winter 



Winter attendance at breeding stands is well documented 

 for California (figs. 10, 11). For example, Sander (1987) 

 detected murrelets on 66 percent of 53 mornings surveyed 

 between January and mid-March at a site in northwestern 

 California. Carter and Erickson (1988) also report on the 

 detection of murrelets from January through March at Big 

 Basin State Park (central California) over several years. 



Murrelets have also been detected at forest stands during the 

 winter in Oregon (Nelson, pers. comm.), Washington (Hamer, 

 pers. comm.), and southeastern Alaska (Naslund, unpubl. 

 data; Walsh, pers. comm.). 



At the three sites in northwestern California, O'Donnell 

 (1993) found that mean numbers of detections per survey 

 during the winter months (November through February) ranged 

 from nine to 24 percent of mean levels in July, with detection 

 numbers in November consistently the greatest in this period. 

 Naslund (1993b) found that mean numbers of detections for 

 winter surveys ranged from 35 to 80 percent of mean summer 

 detection levels for five sites in central California (fig. 12). 

 Doerr and Walsh noted similar differences between winter 



120 



USDA Forest Service Gen. Tech. Rep. PS W- 152. 1995. 



