Carter and Stein 



Chapter 9 



Molts and Plumages 



Most recently-fledged juveniles occurred at sea in July and 

 August in Barkley Sound (Carter 1984, Guiguet 1971), 

 although recently-fledged and older juveniles occurred there 

 into early October when observations ceased (fig. 4). 



To project possible timing of molt for other populations 

 in relation to Barkley Sound, we have summarized the earliest 

 and latest possible fledging dates for Marbled Murrelets in 

 different areas from British Columbia to California. Less is 

 known about the average and latest fledging dates (but see 

 Hamer and Nelson, this volume a). At Langara Island, British 

 Columbia, Sealy (1974, 1975a) reported the first young on 

 the water on 6 and 7 July in 1970 and 1971, respectively. In 

 all of British Columbia, juveniles have been observed at sea 

 between 28 May and 5 October (Rodway and others 1992). In 

 Washington, the earliest known nest fledging date is 22 June 

 1993 (Ritchie, pers. comm.). A juvenile collected on 3 August 

 1950 in the San Juan Islands, Washington, still had an egg 

 tooth (Leschner and Cummins 1992a). In Oregon, juveniles 

 have been observed at sea as early as 15 June (Hardin, pers. 

 comm; Nelson, pers. comm.; Strrr.g and others 1993). Inland 

 records of fledglings in California occur from 12 June to late 

 September whereas recently-fledged juveniles have been found 

 at sea as early as 1 June (Carter and Erickson 1988, 1992; 

 Carter and Sealy 1987b). In general, nesting appears to occur 

 slightly earlier, but over the same general period from late 

 April to September, in the southern part of its range. Thus, the 

 timing of molt would not be expected to vary much throughout 

 this area in relation to the timing observed at Barkley Sound, 

 British Columbia, in 1979-1980 (fig. 4). 



In Barkley Sound, British Columbia, pre-basic molt 

 extended over a long period from mid-July to at least late 

 November (fig. 4). The first bird undergoing pre-basic wing 

 molt was collected on 24 July 1980 (Carter 1984). Whereas 

 some collected birds had almost completed wing molt by 

 mid-September, others that were still molting in early October 

 would not have completed remigial molt until November 

 (Carter, unpubl. data). Murrelets examined by Sealy (1975a) 

 on 20 July at Langara Island had begun body molt on their 

 capital and spinal tracts, but the remiges and rectrices had 

 not begun to molt when observations ceased on 12 August. 

 Kozlova (1957) stated that the complete molt of adult 

 American Marbled Murrelets occurs in September and October 

 and may extend into November, but she did not give the 

 geographic locations of the specimens examined. She also 

 noted that an Asian Marbled Murrelet collected in the Sea of 

 Okhotsk on 31 August had already shed its flight and tail 

 feathers but that other birds obtained in late August on the 

 east coast of Kamchatka showed no traces of molt. Stresemann 

 and Stresemann (1966) noted a rapid molt of the flight 

 feathers that occurred between early August and late October, 

 after examining specimens mainly from California. The 

 closely related Kittlitz's Murrelet also undergoes a flightless 

 pre-basic molt in Alaska between August and October (Sealy 

 1977). Only a few other references to molting Marbled 

 Murrelets have been made. Smith (1959) noted a bird "in 

 changing plumage" drowned in a fisherman's net at Cohoe 



Beach, Alaska, on 22 August 1959. DeBenedictis and Chase 

 (1963) noted one bird "in molt" on 27 July 1963 between 

 Santa Cruz and Pigeon Point, California. Gill and others 

 ( 1 98 1 ) noted two flightless adults in Nelson Lagoon, Alaska, 

 on 3 September 1977. On 1 September 1992, eight murrelets 

 were collected in Mitrofania Bay, Alaska (Piatt, pers. comm.; 

 Pitocchelli, pers. comm.): four birds were in alternate plumage 

 (three with bare brood patches and one with a regressing 

 brood patch), two birds were well into pre-basic molt and 

 two birds were recently-fledged juveniles (with neck bands 

 and egg teeth). In general, it appears that the timing of pre- 

 basic molt follows breeding phenology throughout their range 

 in North America. Large numbers of molting birds occur in 

 museum collections which still need to be summarized to 

 confirm this generalization (Carter, unpubl. data; Becking, 

 pers. comm.). 



Failed breeders or stressed adult birds may initiate an 

 unusually rapid body molt much earlier than the rest of the 

 population. At Langara Island, British Columbia, Sealy 

 (1975a) collected an adult female on 9 July 1971 with a fully 

 developed brood patch and a flaccid ovary. This bird had 

 already undergone a nearly complete body molt into basic 

 plumage, without having yet started wing molt. 



Timing of Pre- Alternate Molt 



The timing of pre-alternate molt is more poorly known 

 than for pre-basic molt and appears to vary between breeding 

 adults and subadults. For the American Marbled Murrelet, 

 Kozlova (1957) stated that the incomplete pre-altemate molt 

 began in April and is completed by late May. Molt may be 

 delayed until June in first-year birds. One male, collected on 

 31 May in the Diomede Islands, had many growing alternate 

 plumage feathers (evident through active blood-filled papillae) 

 on the upper parts, whereas most of the rest of the body was 

 in basic plumage. This bird was collected north of the current 

 breeding range for the species (Sealy and others 1982). It is 

 possible that this bird was not molting in the usual pattern. 

 Sealy (1975a) noted a slight delay in the pre-alternate molt 

 in subadult murrelets at Langara Island, British Columbia. 

 Both adults and subadults returned to Langara Island in late 

 April. Most adults were in alternate plumage whereas 

 subadults were still in basic plumage, although actively 

 molting on their capital and spinal tracts. All subadults 

 eventually achieved alternate plumage by late May (Sealy, 

 pers. comm.). In Barkley Sound, British Columbia, two of 

 45 birds in alternate plumage were considered to be subadult 

 non-breeders because they lacked brood patches and had 

 small gonads in June and July (Carter 1984). No birds in 

 basic plumage were observed in Barkley Sound from early 

 May to late July (Carter, unpubl. data). Occasional summer 

 sightings of murrelets in basic plumage have been reported 

 to Carter from various areas along the west coast of North 

 America but none have been confirmed with specimens or 

 photographs. Museum specimens must be examined to further 

 confirm that all adult birds (including first-year birds) attain 

 the full alternate plumage during the breeding season. 



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



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