Nelson and Hamer 



Chapters 



Nesting Biology and Behavior 



Table 4 Dates and timing of observed Marbled Murreletfledgingsfrom nests by state and 

 province 1 



1 Data from Hamer and Cummins 1991; Hirsch and others 1981; P. Jones, pers. comm.: 

 Nelson and Peck, in press; Singer and others, in press. 



2 Chick fledged between 2050 and 0700 hours. 



Many of these grounded fledglings may be unable to take 

 flight again or make it to the ocean by other means. Once 

 juveniles reach the ocean they are thought to be independent 

 and not attended either parent contrary to the suggestion of 

 Ydenberg (1989). 



Chick Behavior 



Chicks remain motionless or sleep 80-94 percent of the 

 time on the nest (n = 8 chicks) (Hamer and Cummins 1991; 

 Naslund 1993a; Nelson and Peck, in press). Other behaviors 

 include standing, turning, shifting position, preening, 

 stretching, flapping, pecking at the nest substrate or the tree 

 limb, food begging in the presence of adults, and snapping at 

 insects. Behaviors such as wing flapping and preening increase 

 markedly in the week prior to fledging. 



On the two evenings prior to fledging, chicks are very 

 active (Hamer and Cummins 1991; Ritchie, pers. comm.; 

 Singer and others, in press). Behaviors during this time 

 include continual rapid pacing on the nest platform, frequent 

 vigorous flapping of the wings, repeated peering over the 

 edge of the nest platform, rapid nervous head movements, 

 and constant preening. After a vigorous session of wing 

 flapping, young birds sometimes hold their wings outstretched 

 and vibrate them rapidly, giving the appearance of shivering 

 wings. These behaviors begin in late afternoon or minutes 

 before sunset, and continue until dark or until the bird fledges. 



Low light levels may induce fledging. After a captive 

 reared chick fledged from an artificial nest platform in the 

 dark, it was placed back on the platform and the room 

 brightened by artificial light (Hamer and Cummins 1991). 

 The chick immediately sat motionless and ceased all activity. 



When the room was darkened again by turning off the light, 

 the chick immediately began the pre-fledging behaviors 

 described above and fledged a second time. 



Feeding Frequency, Behavior, and Prey Species 



Adults return to feed young up to eight times daily ( x = 

 3.2, s.e. = 0.4, n = 10 nests) (Hamer and Cummins 1991; 

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

 comm.; Nelson and Peck, in press; Simons 1980; S.W. Singer, 

 pers. comm.) (table 5). Chicks are usually fed at least once a 

 day for the 27-40 days they are on the nest, although the 

 frequency is variable and sometimes decreases prior to fledging. 

 The last feeding prior to fledging occurs between 5 minutes 

 (Singer and others, in press) and 2.5 days (Hamer and Cummins 

 1991) before the young munelet leaves the nest 



The timing of dawn feedings is more variable than 

 incubation exchanges. First dawn feedings occur from 37 

 minutes before to 65 minutes after official sunrise ( x = 6.0, 

 s.e. = 3.7, n = 68 feedings at 13 nests) (Hamer and Cummins 

 1991; Kerns, pers. comm.; Naslund 1993a; Nelson and Peck, 

 in press; S.W. Singer, pers. comm.) (fig. 1, table 6). Similar 

 to incubation exchanges, weather and light conditions 

 influence the arrival times of the adults, and feedings often 

 occur later on rainy or cloudy days (Naslund 1993a, Nelson 

 and Peck, in press). Second morning feedings occur from 18 

 minutes before, to 225 minutes (1009 hrs) ( x = 53.7, s.e. = 

 9.6, n = 40 observations at 13 nests) after, official sunrise. 

 Other feedings take place during the day between the hours 

 of 1100 and 1700 (Hamer and Cummins 1991; P. Jones, 

 pers. comm.; Kerns, pers. comm.; Naslund 1993a; Nelson 

 and Peck, in press; Singer and others 1991)(/ig. 7). Dusk 



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



61 



