Nelson and Hamer 



Chapter 5 

 Table 3 Mean length of incubation exchanges at Marbled Murrelet nests by state 1 



Nesting Biology and Behavior 



1 Data from Nelson and Peck, in press; S.W. Singer, pers. comm. 



2 Incubation exchanges were not observed in British Columbia and Washington. 



3 Data from Alaska were not available. 



press; Simons 1980). Chicks are semi-precocial at hatching, 

 and weigh approximately 32.0-34.5 g (n = 2 chicks) (Simons 

 1980, Hirsch and others 1981). They are covered with a 

 dense yellowish down, sprinkled evenly with irregular dark 

 spots (brown and black), except on the head where spots are 

 concentrated in large patches, and on their bellies which are 

 covered with a dense, pale grey down (Binford and others 

 1975, Simons 1980). 



Adults usually brood the chick for 1 to 2 days after 

 hatching ( = 4 nests) (Nelson and Peck, in press; Simons 

 1980; S.W. Singer, pers. comm.), possibly until the chick 

 reaches homeothermy. However, Naslund (1993a) recorded 

 intermittent brooding by adults after daytime and evening 

 feedings at least 3 days after hatching. Naslund (1993a) 

 suggested that the increased brooding may have occurred to 

 protect the chick from predators in the vicinity of the nest. In 

 addition, in British Columbia, Eisenhawer and Reimchen 

 (1990) presented circumstantial evidence that adults returned 

 at night to brood young chicks. 



During brooding, adults are active and restless, regularly 

 standing, turning, and repositioning themselves on the chick. 

 Adults do not remove the eggshell from the nest cup, therefore 

 pieces that do not fall out accidentally remain in the nest cup 

 and often are crushed into the nest material by adult and 

 chick activity. 



During the first 6 days after hatching, droppings from 

 the chick begin to accumulate around the perimeter of the 

 nest cup (adults are not known to defecate at the nest). By 

 the time the chick fledges, the fecal ring can be up to 5 1 mm 

 thick. Odor (ammonia and fish) from fecal material can be 

 detected by humans from up to 2 m away. 



Murrelet chicks grow rapidly compared to most alcids, 

 gaining 5-15 g per day during the first 9 days after hatching 

 (n = 2 chicks) (Hirsch and others 1981; Simons 1980). As 

 chicks age, the Juvenal plumage begins to develop beneath 

 the down; both feather types grow from the same sheath. 

 By day 17, the wing coverts have emerged and down is 

 missing from the forehead and around the mandibles (n = 5 

 chicks). By day 21, chicks lose most of their belly down, 

 and by day 26, up to 20 percent of body down disappears. 



Twelve to 48 hours prior to fledging, the murrelet chick, by 

 preening, scratching, and wing flapping, removes the 

 remaining down, revealing their black and white Juvenal 

 plumage (n = 10 chicks) (Hamer and Cummins 1991; 

 Hirsch and others 1981; P. Jones, pers. comm.; Nelson and 

 Peck, in press; Simons 1980; Singer and others 1992, in 

 press). This pattern of down loss and feather development 

 is unique among alcids, except the closely related Kittlitz's 

 Murrelet (Brachyramphus brevirostris). 



Wing length increases rapidly in the last 4 days prior 

 to fledging, and at fledging the chicks wings are 103-144 

 mm long (86 percent of adult wing length) (Hamer and 

 Cummins 1991; Hirsch and others 1981; Sealy 1975a; Simons 

 1980). Chicks fledge at age 27-40 days (Hirsch and others 

 1981; Nelson and Peck, in press; Simons 1980). At this time 

 they still possess an egg tooth, and weigh an average of 

 146.8-157.0 g (s.e. = 3.6-9.5, n = 4-9), which is 63-70 

 percent of adult (222 g) weight (Hamer and Cummins 1991; 

 Hirsch and others 1981;Sealy 1975a; Simons 1980). Fledging 

 takes place at dusk, between 1 1 and 55+ minutes after 

 official sunset (Hamer and Cummins 1991 ; Hirsch and others 

 1981; P. Jones, pers. comm.; Nelson and Peck, in press; 

 Singer and others, in press) (table 4). 



Chicks are thought to fly directly from the nest to the 

 ocean (Hamer and Cummins 1991; Quinlan and Hughes 

 1990; Sealy 1975a). Hamer and Cummins (1991) radio- 

 tagged a juvenile Marbled Murrelet on a nest in Washington, 

 37 km inland, and monitored its flight to the ocean. The 

 chick fledged in the evening and was found 1 8 hours later, 

 100 m from shore and 2 km north of a direct east- west line 

 between the nest and Puget Sound. The juvenile flew directly 

 to the ocean and did not spend any time in the vicinity of the 

 nest. However, several fledglings have been observed 

 swimming in creeks in California and Washington (Hamer 

 and Cummins 1991; Miller, pers. comm.). It is not known if 

 these fledglings fell from nests, became grounded on their 

 maiden flight to the ocean, or were actually trying to reach 

 the ocean by swimming the creek. Numerous fledging birds 

 in North America appear to have become grounded during 

 flights to the Pacific (Nelson and Hamer, this volume b). 



60 



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



