Carter and Stein 



Chapter 9 



Molts and Plumages 



1Z FTP- I 



Figure 2 Pre-alternate molt sequence in Marbled Murrelets. Museum specimens are ordered to reflect changes in ventral plumage during pre- 

 alternate molt. The far left specimen is in basic plumage and the far right specimen is in alternate plumage. Collection dates of specimens from left 

 to right: 22 February 1 900, 27 February 1 907, 1 8 February 1 907, 30 March 1907, 18 February 1907, 20 February 1896, 27 February 1907, 26 March 

 1907. Specimens are housed at the California Academy of Sciences, San Francisco, California. Photo taken by H.R. Carter. 



sides of the neck, and underparts are covered with white 

 feathers that are edged with broad dark-brown margins (fig. 

 2). These dark margins take up about half of each feather. 

 The flanks are almost entirely dark brown, the upper wing 

 coverts are dark brown with occasional narrow white edges, 

 and the under wing coverts and axillaries are brownish grey. 

 The rectrices are brownish black, occasionally with narrow 

 white margins and brownish dots on the outer rectrices. 

 There are no known differences in plumage appearance 

 between sexes or ages of adult birds. However, in some 

 European alcids, first-year birds may retain certain upperwing 

 coverts, leading to a visible contrast between older, retained 

 feathers against newer, replaced feathers (Pyle, pers. comm.). 

 Such detailed examinations are required for the Marbled 

 Murrelet to unveil such possible distinctions when examining 

 birds in the hand. 



Murrelets in basic plumage closely resemble the plumage 

 of several other alcids, being "dark above" and "light below." 

 The basic plumage is often considered closer to an older, 

 ancestral plumage. The evolution of the cryptic alternate 

 plumage is an obvious adaptation for nesting solitarily in 

 old-growth forests (Binford and others 1975). It is likely 

 that the Marbled Murrelet originally evolved its cryptic 



plumage by using similar nesting habitats as the closely- 

 related Kittlitz's Murrelet (B. brevirostris). The latter species 

 also attains a very cryptic alternate plumage for nesting 

 solitarily on mountain scree slopes in Alaska and Russia up 

 to 100 km inland from the ocean (Day and others 1983). 

 However, the alternate plumage of the Marbled Murrelet is 

 darker overall and, unlike the Kittlitz's Murrelet, the rust- 

 tipped back feathers of Marbled Murrelets closely match 

 the bark of typical nest trees. While about 3 percent of the 

 Alaskan population of Marbled Murrelets nests solitarily on 

 the ground (Day and others 1983, Mendenhall 1992, Piatt 

 and Ford 1993), it is unclear whether they represent remnant, 

 ancestral ground-nesting behavior or a more recent 

 redevelopment of such behavior. In any case, the cryptic 

 alternate plumage was one preadaption that may have allowed 

 Marbled Murrelets to originally colonize and nest in old- 

 growth forests. 



Distinctions between the plumages and other char- 

 acteristics of the American Marbled Murrelet (B. m. 

 marmoratus) and the Asian Marbled Murrelet (B. m. perdix) 

 can be found in several papers (Erickson and others 1994; 

 Kozlova 1957; Sealy and others 1982, 1991; Sibley 1993). 

 Recent evidence indicates that the Asian Marbled Murrelet 



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



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