BIRDS OF NORTH AND MIDDLE AMERICA. 147 



Long-winged, small-billed terrestrial finches, with the maxilla much 

 narrower, vertically, than- the mandible, the gonj'sverj' short (little if 

 anj' more than half the lateral length of the mandible), the hind claw 

 long and stronglj^ curved, and the plumage largely (sometimes chiefly) 

 white. 



Bill peculiar in shape, the maxilla being much shallower than the 

 mandible and the gonys very short (little if any more than half the lateral 

 length of the mandible) ; maxillary tomium slightly concave anteriorly, 

 then almost imperceptibly convex, with an abrupt basal deflection 

 beginning directly beneath the nostril. Nostrils quite concealed bj^ a 

 distinct appressed tuft of antrorse latero-frontal plumules. "Wing 

 long (nearly five times as long as tarsus) and pointed (ninth, eighth, 

 and seventh, usuallj' the ninth, primary longest); primaries exceeding 

 secondaries bj- twice the length of the tarsus; tertials not elongated. 

 Tail about three-fifths as long as wing, about two-thirds hidden bj' 

 the coverts, emarginated, the middle pair of rectrices pointed at tip. 

 Tarsus slightly longer than middle toe with claw, its scutella indistinct 

 or obsolete on outer side; lateral claws scarcely reaching base of middle 

 claw; hind claw about as long as its digit, slender, arched. 



Coloration. — Prevailing color white, the inner webs of rectrices 

 (except sometimes of two middle pairs) entirely so. Adult males in 

 simimer with head, neck, entire lower parts, lower back, rump, second- 

 aries (except, sometimes, tei'tials), and greater part of wing-coverts 

 entirely pure white; back and scapulars black or white; bill entirely 

 deep black. [In winter, the upper parts, sides of head, and chest 

 washed with rusty; bill j^ellow, the extreme tip dusky.) Adult females 

 smaller than males, the upper parts entirely streaked, the wings with 

 much less white, etc. Young: Pileum, hindneck, back and rump dull 

 grayish, indistinctly streaked with darker; lower parts dull whitish, 

 more or less tinged anteriorly with grayish (sometimes uniformly 

 grayish on throat, chest, etc.). 



Bcmge. — Arctic and subarctic districts of northern hemisphere (south- 

 ward in winter). 



KEY TO THE SPECIES AND SUBSPECIES OP PASSERINA. 



a. .nner webs of primaries witli much less than basal half white; adults with back 

 and scapulars black or at least with central portion of feathers extensively black. 

 h. Smaller, with relatively shorter bill (adult male averaging, wing 110:49, tail 66.04, 

 exposed culmen 10.41, depth of bill at base 6.10, tarsus 21.84, middle toe 

 14.22; adult female averaging, wing 102.11, tail 63.50, exposed culmen 10.16, 

 depth of bill at base 6.10, tarsus 21.34, middle toe 14.22). (Circumpolar, 

 but not on islands of Bering Sea or Aleutian chain.) 



Passerina nivalis nivalis (p. 148) 



hb. Larger, with relatively longer bill (adult male averaging, wing 113.03, tail 70.87, 



exposed culmen 12.70, depth of bill at base 6.60, tarsus 23.11, middle toe 



14.99; female adult averaging, wing 106.68, tail 65.02, exposed culmen 12,19, 



depth of bill at base 6.60, tarsus 22.61, middle toe 14.73). (Pribilof, 



