Naslund and O'Donnell 



Chapter 12 



Daily Patterns of Activity at Inland Sites 



Table 1 Mean detection times ( x ) and their standard deviation isdi, in minutes, relative to sunrise of Marbled Murrelet detection categories at Big Basin 

 Redwoods State Park. California from 1989-1991, and at \aked Island, Alaska during 1992. Results of Tutey-Kramer range teas are shown. Means with 

 different letters (in parentheses) are significantly (P < 0.05) different from each other 



1 Naslund (unpubl. data) 

 - Kuletz (pers. comm. i 



3 Wings heard only, not seen 



4 Heard calling, not seen 



5 Seen and heard calling 



6 Seen, not calling 



(lable 7). In British Columbia, solitary calls were most frequent 

 before sunrise (Manley 1992). Murrelets making only wing 

 sounds were heard earlier than those heard vocalizing or 

 those seen (table 1). This pattern was consistent year-round 

 but was significant only during the breeding seasons in 

 California and Alaska. Silent murrelets were also seen 

 relatively earlier in Alaska than in California. This may 

 partially be a function of greater light levels before dawn in 

 Alaska, thereby making murrelets easier for observers to 

 see. In British Columbia. Manley (1992) found that the 

 occurrence of silent murrelets (including both single birds 

 and pairs) peaked 20 minutes before sunrise. 



Discussion 



Daily Patterns of Activity and Behaviors 



Murrelets exhibit a primary period of inland activity 

 around dawn and a secondary period around dusk. That 

 murrelets are most active during the low light levels of dawn 

 and dusk presumably reflects adaptation to predation pressures 

 in the forest. Nesting murrelets and their chicks and eggs are 



vulnerable to a variety of avian predators including corvids 

 and raptors (Brown, pers. comm.; Marks and Naslund 1994; 

 Naslund and others, in press; Nelson and Hamer 1992, this 

 volume b; Singer and others 1 99 1 ). Crepuscular activity also 

 allows for maximum diurnal foraging time. 



Variation in activity levels during the day appears to 

 mirror aspects of murrelet nesting biology. Murrelets exchange 

 incubation dudes and exhibit peak feeding rates of young 

 chicks around dawn (Hamer and Cummins 1991; Naslund 

 1993a; Nelson and Hamer, this volume a; Nelson and Hardin 

 1993a; Nelson and Peck, in press; Singer and others 1991, 

 1992). Murrelets also sometimes exhibit flight behaviors 

 around nests and feed chicks around dusk. They visit nests 

 with young chicks infrequently mid-day, though diurnal 

 feedings increase when chicks get older (Fortna, pers. comm.; 

 Hamer and others 1991; Naslund 1993a; Nelson and Hamer, 

 this volume a; Singer and others 1991). 



Low detection levels at dusk may result from temporal 

 differences in the composition and behavior of murrelets at 

 inland sites. Fewer nonbreeders may fly inland during the 

 evening activity period. Murrelets appear to fly silently while 



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



133 



