4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



The specimen study showed the hermit thrush to be quite variable 

 in size and color. Within any given breeding population, male hermit 

 thrushes average larger, and in most cases significantly larger, than 

 females in wing length (fig. 1). On the other hand, the bills of females 

 tend to be equal to or longer than those of males (fig. 2). When shown 

 as a ratio, the relatively longer bills of females in proportion to wing 



111 



110 - 



105 



<f (43) 



100 



(24) M«M 



Q (l5) (55) 



43- 



TJ 9 



(32) 



(2D (8) (f 



cf 9 



(22) 



9 



43- 



-fr 



-frn 



(16) 

 (23) 9 



(18) (f 

 9 



.i} 



■a- 



•s- 



I"? v 



'-E3- 



(id 

 9 



■A- 



(id 



(9) (f 



9 



-EH} 



(6) 



9 



/SL- 

 ITI (Tl. 



Figure 1. — Wing 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 = 1, auduboni; 2, sequoiensis; 

 3,faxoni; 4, euborius; 5, crymophilus; 6, oromelus; 7, vaccinius; 8, guttatus; 9, nanus; 

 10, slevini.) 



length becomes more apparent (table 1). In nine out of 10 popula- 

 tions, female specimens have proportionately longer bills on the aver- 

 age than males. Within any given breeding population, no differences 

 in color correlated with sex were detected. There are two slightly 

 differentiated color phases (rufescent and grayish) that may appear 

 in any population (Oberholser, 1932). In the present study these 

 phases, noted in all populations, seemed to be most distinct among 

 eastern birds. The speckled dorsal plumage of juveniles is quite dif- 



