no. 3637 HERMIT THRUSH — ALDRICH 5 



ferent from the uniformly colored upper parts of adults. Some of the 

 speckled ju venal feathers among the upper wing coverts are carried 

 over after the postjuvenal molt, even into the following breeding sea- 

 son, making possible the recognition of first-year birds up to the time 

 of the first postnuptial molt. This subadult plumage (with the scat- 

 tered juvenal feathers among the wing coverts) is very slightly more 

 rufescent and paler on the average than the fully adult plumage 

 when equivalent color phases of each are compared in series. Wear of 



i — no 

 o' 



9 (6) 



i — i (15) 



(45) (23) 

 J 9 



(6) 



9 



--{} 



4-. (32) 



(18) isa H9) 



o o V 



& 



{} 



(24) 



12 — 



(20) 



a* 



(15) 

 O 



(4) 



9 



(9) H2' 



n 9 cf 



(8) (6) 

 9 d 



f 



(6) 



■ 4 



no 



9 



■J- 





101— 

 m <n. 



Figure 2. — Bill lengths of subspecies of Catharus guttatus, showing ranges (vertical lines), 

 means (horizontal), and two standard errors on either side of the means (rectangles). 

 (Numbers in parens = sample sizes. Numbers at bottom = l, slevini; 2, sequoiensis; 3, audu- 

 boni; 4, crymophilus; S,faxoni; 6, oromelus; 7, euborius; 8, vaccinim; 9, nanus; 10, guttatus.) 



feathers causes color to be duller, more grayish, and sometimes paler 

 in the breeding season than in fresh autumn plumage. 



Although McCabe and McCabe (1932) minimized the reliability 

 of color characters hi distinguishing populations of hermit thrushes, 

 specimens taken at the same season of the year reveal marked geo- 

 graphical differences in color (shade and hue) that are far greater 

 than the differences due to age or color phase. East of the Rocky 

 Mountains, color of breeding birds is relatively uniform over a vast 

 area, but west the of Rockies, particularly along the coast, much 

 geographical variation occurs in a relatively limited area, and changes 



