Chapter 11 



Patterns of Seasonal Variation of Activity of Marbled 

 Murrelets in Forested Stands 



Brian P. O'Donnell 1 



Nancy L. Naslund 2 C. John Ralph 3 



Abstract: Determining the annual cycles of Marbled Murrelet 

 (Brachyromphus marmoratus) behavior is crucial both for under- 

 standing the life history and for management of this species. In 

 this paper we review available information on the annual patterns 

 of behavior in forests throughout its range, with special emphasis 

 on California. Data were derived from standardized forest 

 surveys. Murrelet activity peaks during the summer (breeding 

 season), is lower during the winter (non-breeding season), and 

 absent or very low during transition periods (pre-alternate and 

 pre-basic molts). Murrelets are regularly detected at some breed- 

 ing stands even in the non-breeding season, however, birds are 

 rarely observed flying through or below the forest canopy during 

 this period. Vocalizations and flock size exhibit seasonal varia- 

 tion as well. While certain aspects of seasonal activity and behav- 

 ior patterns conform with our limited understanding of its life 

 history, much of the species' behavior within the forest remains a 

 mystery. Current guidelines for monitoring the Marbled Murrelet 

 at inland sites restrict surveys for management purposes to the 

 breeding season. 



Determining the annual cycles of Marbled Murrelet 

 (Brachyramphus marmoratus) activity and behavior at inland 

 sites is important for an understanding of this species' life 

 history and its management. In order to assess the probable 

 presence of nesting murrelets in a forest stand, we must 

 first know how their behavior in the forest changes through 

 the year, and what these seasonal changes tell us about its 

 biology. With this information in hand, we can then 

 determine how best to develop a survey protocol. In this 

 chapter we review available information on the annual 

 cycles of activity and behavior in the forest. We draw 

 heavily from the results of two studies in California (Naslund 

 1993,b; O'Donnell 1993). Data in these studies were 

 collected using intensive survey techniques (Paton, this 

 volume; Paton and others 1990; Ralph and others 1994). 

 Additional information, derived from general and intensive 

 survey techniques, are reported from studies throughout 

 the range of the species. As the measure of activity we use 

 the "detection": the observation of one or more birds acting 

 in a similar manner. 



1 Wildlife Biologist, Pacific Southwest Research Station, Redwood 

 Sciences Laboratory, USDA Forest Service, 1700 Bayview Drive, Arcata, 

 CA 95521 



2 Wildlife Biologist, U.S. Fish and Wildlife Service, U.S. Department 

 of Interior, 101 1 E. Tudor Road, Anchorage, AK 99503 



3 Research Biologist, Pacific Southwest Research Station, Redwood 

 Sciences Laboratory, USDA Forest Service, 1700 Bayview Drive, Arcata, 

 CA 95521 



Variation in Detection Levels 



Numbers of detections vary dramatically through the 

 year, and in general, are greatest during the summer months. 

 Detection levels were compared between months through 

 the year in two studies in California. Naslund (1993a) 

 compared detections at two sites in central California between 

 three periods: (1) breeding season April through July; (2) 

 transition periods March, and August through October; 

 and (3) winter November through February. She found 

 detections were significantly greater during the summer period 

 (table 1). O'Donnell (1993) also found significant differences 

 between months at each of three sites in northwestern 

 California. He found that mean numbers of detections per 

 survey were greatest in July at all sites (fig. 1). Mean numbers 

 of detections per survey in April through June ranged from 

 28 to 62 percent of those in July, and mean detections per 

 survey in May and June were always intermediate between 

 those in April and July. 



Murrelet detection levels also tended to peak during 

 July and early August in most locations to the north of 

 California. In Oregon, Nelson (1989) found the greatest 

 detection levels from 12 July to 9 August at sites (fig. 2). She 

 also noted an early period of high activity in late May and 

 early June. The two activity peaks were detected during both 

 dawn and evening surveys. During the 1990 breeding season 

 in northwestern Washington, Hamer and Cummins (1990) 

 noted 60 percent of all detections occurred between 25 June 

 and 27 July (fig. 3). Numbers of detections per survey were 

 greatest from mid- July through the end of the month. In the 

 following summer, 77 percent of all detections were recorded 

 between 8 July and 1 1 August, with the greatest numbers of 

 detections per survey occurring in the week of 22 July 

 (Hamer and Cummins 1991) (fig. 4). During 1990, weekly 

 mean numbers of detections of murrelets peaked in the last 

 week of July at two sites in the Queen Charlotte Islands, 

 British Columbia (Rodway and others 1993b) (figs. 5, 6). 

 However, detection levels at sites on Vancouver Island, 

 British Columbia, reached their greatest levels in late June 

 (Manley and others 1992) (fig.7). At a site on Mitkof Island, 

 in southeastern Alaska, where Doerr and Walsh have 

 conducted one to three morning surveys each month since 

 December 1992, the numbers of detections peaked in July 

 (Doerr, pers. comm.; Walsh, pers. comm.). Kuletz and others 

 (1994c) found that seasonal peaks of murrelet activity in 

 Prince William Sound, Alaska, were similar to those reported 

 for the more southerly areas of the species' distribution (figs. 

 8, 9). They also noted an early period of greater activity in 



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



117 



