304 Birds of Colorado 



feet from the entrance, which was barely large enough 

 for the Wren to squeeze through much less the Cow-bird. 

 Aiken informs me he once found in Wet Mountain 

 Valley a Yellow Warbler's nest, built in three stories, 

 the lower one of which contained eggs of the Cow-bird ; 

 it is presumed that the successive stories were built 

 by the Warblers to avoid hatching the Cow-bird eggs. 

 The eggs of the Cow-bird are very strongly shelled ; 

 whitish in colour, profusely speckled with reddish- 

 brown ; they average -84 x '65 in measurement. 



Genus XANTHOCEPHALUS. 



Medium-sized birds — wing imder 6 — with a stout, conical bill, shorter 

 than the head, the culmen straight, not decurved ; nostril oval, over- 

 hung by a prominent operculum ; wings long and pointed ; the outer 

 (ninth) primary usually the longest ; tarsus stout, nearly twice as long 

 as the culmen ; plumage black or dusky, and yellow. 



The Yellow-headed Blackbird is the only species assigned to this genus. 



Yellow-headed Blackbird. Xanthocefhaliis xanthocephalus. 



A.O.U. Checklist no 497— Colorado Records — Baird 58, p. 531 

 (Z. icterocephaltis) ; Aiken 72, p. 202 ; Henshaw 75, p. 315 ; Scott 

 79, p. 94 ; Minot 80, p. 230 ; Allen & Brewster 83, p. 193 ; Drew 

 85, p. 16; Beckham 85, p. 142; Thome 88, p. 112; Morrison 89, 

 p. 148 ; Lowe 92, p. 101 ; Cooke 97, pp. 18, 93, 211 ; Keyser 02, p. 141 

 Dille 03, p. 74 ; Henderson 03, p. 236 ; 09, p. 234 ; Warren 06, p. 22 

 08, p. 22 ; 09, p. 15 ; Markman 07, p. 157 ; Oilman 07, p. 156 

 Rockwell 08, p. 169 ; Hersey & Rockwell 09, p. 118. 



Description. — Male in summer — Head, neck and chest bright orange- 

 yellow ; a patch round the eye and base of the bill and the whole of 

 the rest of the plimiage black ; a white patch on the base of the wing 

 involving the primary and some of the greater coverts ; a rather 

 indistinct yellow anal-patch ; iris brown, biU and legs black. Length 

 10-5; wing 5-75 ; tail 4-65 ; culmen -85 ; tarsus 1-50. 



In winter the yellow of the crown and hind-neck is obsciu-ed by dusky 

 tips to the feathers. The female is much smaller than the male (wing 

 about 4-5) ; it is dark sepia-brown in colour with the superciliary stripe, 

 chin, throat and upper-breast dull yellow, and the lower-breast streaked 

 with white ; no white wing-patch. The young male resembles the 

 female, but is larger and somewhat darker, both as regards the brown 

 and the yellow. 



