598 



BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



frequently streaked mesially (more or less broadly) with dusky;" 

 middle wing-coverts broadly tipped or terminally margined (more or 

 less distinctly) wdtli brownish gray; greater coverts edged with brown- 

 ish gray and tipped with the same or paler brownish gray; secondaries 

 edged wath pale brownish gray or dull white; outer web of lateral 

 rectrix edged (more or less broadly) with white; axillars and under 

 wing-coverts dark sooty gray or brownish slate, their outer webs 

 mostly white and inner webs extensively white at tip; inner webs of 

 remiges edged with pale brownish gray; bill black, the mandible 

 more brownish, especially toward base; iris brown; legs and feet 

 brownish black. 



Young. — Similar to adults, but general color more sooty, the 

 feathers of lower back, hinder scapulars, rump, and upper tail-coverts 

 indistinctly tipped with pale brownish; wing-coverts tipped with 

 cumamon or light rusty; w^hite of under parts suffused along border 

 with brown or rusty. 



Adult maif.— Length (skins), 152-181 (165); wing, 84-96 (91.5); 

 tad, 71-84 (79.9); exposed culmen, 14-16.5 (15.5); tarsus, 17.5-19.5 

 (18.4); middle toe, 9.5-11 (10.5).^ 



Adult female.— ljej\gi\\ {skms) , 147-176 (160); wing, 81-93.5 (86.5); 

 tail, 68-80 (74.9); exposed culmen, 14-16 (14.9); tarsus, 15.5-18 

 (17.4); middle toe, 9.5-11 (lO.S).*^ 



fl So far as the collection of the U. S. National Museum, including that of the Bio- 

 logical Survey, is concerned, the difference in coloration of the under tail-coverts 

 between specimens from California, Arizona, and western Mexico on the one hand, 

 and those from central, eastern, and southern Mexico on the other, mentioned by Mr. 

 Nelson (Auk, xvii, 1900, 124, 125) certainly exists, with remarkable uniformity; and 

 were it not for Mr. Brewster's later observations on the subject (Bull. Mus. Comp. Zool., 

 xli, 1902, 119) I would unhesitatingly adopt Mr. Nelson's division of the northern repre- 

 sentatives of the species into two forms, S. n. nigricans and S. n. semiatra, since in the 

 series examined the difference is both conspicuous and str'ctly geographic. 



b Twenty specimens. 



c Sixteen specimens. 



