610 



BULLKTIN 50, UNITED STATES NATIONAL MUSEUM. 



GUIRACA CiERULEA LAZULA (Lesson). 

 "WESTERN BLUE GROSBEAK. 



Similar to (r. c. aGndeahnty^mg and tail decidedly longer and color- 

 ation lighter, with \vino--])ands broader; adult male with the blue color 

 lig-hter and less purplish, the wing-bands much ])roader and paler, that 

 across tips of greater coverts usually (when not abraded) 5.08-7.62 

 wide and decidedly paler than the middle covert l)and; white margins 

 to under tail-coverts broader, rarel}", if ever, indistinct; adult female 

 and young with the general coloration paler and decidedly less tawny. 



A<hiJt m.ale.~hn\gih (skins), 149.86-177.80 (162.81); wing, 86.36- 

 96.52 (90.1:2); tail, 66.55-78.71 (70.36); exposed culmen, 13.97-17.78 

 (15.75); depth of bill at base, 12.19-15.75 (13.16); tarsus, 19.30-22.86 

 (20.32); middle toe, 15.75-17.78 (16.76).^ 



Adnlt femaJe.—Langih. (skins), 112.24-165.10 (155.70); wing, 76.71- 

 88.39 (84.58); tail, 61.21-71.12 (66.55); exposed culmen, 13.97-17.27 

 (15.75); depth of bill at base, 12.45-14.73 (13.46); tarsus, 15.49-23.11 

 (20.83); middle toe, 15.49-17.78 (16.51).' 



^ Sixty-five specimens. 



^ Twenty-nine specimens. 



There is a decided average difference in measurements of specimens from separate 

 geographic areas, tliis 1)eing so marked tliat furtlier subdivision may ultimately be 

 deemed necessary. Averages of the series examined are as follows: 



There is also much individual variation among specimens from the same geographic 

 area, one adult female from Oaxaca (Huitzo) having the tarsus only 20.83 mm., 

 while two others from the same State have the tarsus 22.86 and 23.11, respectively. 

 Some specimens from Utah and other parts of the Great Basin agree in small meas- 

 urements, especially of the bill, with California examples and not, as might be 

 expected, with those from Arizona. The average difference in measurementa is not 

 great except in case of the California birds, which have a decidedly smaller bill even 

 than true G. civrulea, though the wing and tail are decidedly longer. The coloration 

 being (juite identical, so far as I am able to see, in specimens from the different areas 

 designated above, I am not disposed to make any subdivision of the Western form. 

 It may, however, eventually prove desirable to do so. 



