Naslund and O'Donnell 



Chapter 12 



Daily Patterns of Activity at Inland Sites 





were higher on cloudy (>80 percent cloud cover) than on 

 clear (<80 percent cloud cover) days in British Columbia. 

 Conversely, highest activity levels and detection rates have 

 been recorded during clear (<25 percent cloud cover) and 

 mostly cloudy (>75 percent cloud cover) mornings in 

 Washington and Oregon (Hamer and Cummins 1990, Nelson 

 1989, Nelson and Hardin 1993a). However, Hamer and 

 Cummins also noted that activity (mean number of detections) 

 was greatest during conditions of light drizzle. 



Other environmental factors also affect murrelet activity. 

 Activity levels were high during periods of low cloud ceiling 

 and decreased with increased wind speed and decreased 

 temperatures during summer in Alaska (Kuletz and others 

 1994c). Mean detection rates were highest during conditions 

 of poor visibility (i.e., low visibility ratings corresponded to 

 days with low cloud ceilings) (Hamer and Cummins 1990). 

 When examining weather effects in more detail, it was found 

 that murrelets in Oregon were most active when it rained at 

 the beginning of the survey, or when it was foggy at the end 

 (Nelson and Hardin 1993a). In Alaska, murrelets sometimes 

 exhibited high activity levels during snowstorms, when cloud 

 ceilings were low and wind was negligible (Naslund, unpubl. 

 data; Piatt, pers. comm.). 



Weather may also influence the occurrence of activity 

 around dusk. Although activity at dusk is infrequent in Alaska, 

 murrelets were detected circling inland on two extremely 

 foggy evenings (Kuletz 1991). 



Variation in Behaviors, Vocalizations, and Group Size 

 During the Morning Activity Period 



Murrelet detections below canopy were more frequent 

 than those above canopy, early in the morning activity period 

 during the breeding season in northern California (fig. 4; 

 O'Donnell, unpubl. data). The opposite was true after sunrise. 

 It appears that this pattern remains intact throughout the 

 year. The mean time that murrelets were seen in nest stands 

 below canopy was significantly earlier than flight activity 

 seen above canopy year-round in central California and 

 during the breeding season in Alaska (table 1). 



Group size of murrelets seen flying in forested stands 

 varies with time of day. In central California and Alaska, the 

 mean time at which different group sizes were observed 

 varied throughout the morning during the breeding and 

 nonbreeding (California only) seasons (table 1). Individuals 

 occurred earliest, pairs somewhat later, and groups (i.e., >3) 

 latest. However, this trend was not apparent during the 

 transitional period. Similar trends have been noted in British 

 Columbia and Oregon. In these regions, most observations 

 before 20 minutes before sunrise were single birds, whereas 

 later detections included larger groups (Manley and others 

 1992, Nelson and Hardin 1993a). 



Numbers of vocalizations made by murrelets also exhibit 

 temporal variation during the morning activity period. Single 

 calls were heard earlier than calls involving >6 calls/detection, 

 although this was only significant during the breeding season 



g 







U. 

 O 



o 



DC 



LJJ 

 Q_ 



20 -i 



15 - 



10 - 



5 ~ 



ABOVE CANOPY, n s 2,636 

 BELOW CANOPY, n = 2,519 



MINUTES BEFORE AND AFTER SUNRISE 



Figure 4 Timing of detections of Marbled Murrelets above and below the canopy relative to 

 sunrise. Data presented are from Lost Man Creek in northwestern California, 1 989-1 991 . n is 

 the number of detections for each behavior class (O'Donnell, unpubl. data) 



132 



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



