BIRDS OF WOETH AND MIDDLE AMEBIOA. 93 



inner side occupying the upper half or more; lateral toes relatively 

 short and weak, their claws falling decidedly short of base of middle 

 claw; basal phalanx of middle toe united to that of outer toe by about 

 half its length, to inner toe by nearly as much. 



Coloration. — Above opaque (not glossy) metallic green, bronze, and 

 violet; under parts, together with auricular region, white. 



Nidification. — Nest in holes of trees or cliffs, composed of fine 

 grasses, feathers, etc. ; eggs immaculate white. 



jRcmge. — Western North America, and southward to Costa Rica. 

 (Monotypic.) 



This genus is related to both Iridojyrocne and Oallichelidon, but is 

 sufficiently distinct. 



KEY TO THE SUBSPECIES OF TACHYCINETA THALASSINA. 



a. Back, etc., metallic (not burnished) green, bronze, or purplish. (Adults.) 

 6. Larger (adult male averaging wing 123.5, tail 50.5; adult female averaging wing 

 113.3, tail 47.2); back and scapulars usually purple (rarely green in female); 

 upper tail-coverts green. (Mexican plateau. ) 



Tachycineta thalassina thalassina, adults (p. 93) 



66. Smaller (adult male averaging wing less than 116, tail 46 or less; adult female 



averaging wing less than 110, tail less than 44) ; back and scapulars usually 



green (very rarely purplish); upper tail-coverts blue, violet, and purple. 



c. Larger (wing averaging 115.2 in adult male, 109.7 in adult female; tail 46 in 



adult male, 43.7 in adult female). ("Western North America, from western 



Texas, New Mexico, Arizona, etc., to the Yukon Valley, Alaska; south to 



Guatemala in winter. ) Tachycineta thalassina lepida, adults (p. 95) 



ce. Smaller (wing averaging 105.2 in adult male, 101.1 in adult female; tail 42.8 

 in adult male, 40.8 in adult female). (Southern Lower California.) 



^Tachycineta thalassina brachyptera, adults (p. 98) 

 aa. Back, together with other upper parts, sooty grayish brown. (Young.) « 



TACHYCINETA THALASSINA THALASSINA (Swainson). 

 MEXICAN VIOLET-GREEN SWALLOW, 



Adtdtmale. — Pileum and hindneck soft bronze-green; back scapulars 

 and lesser wing-coverts soft purplish green to Indian purple; median 

 portion of rump and upper tail-coverts soft dark bottle green, some- 

 times tinged with blue; wings (except lesser coverts) and tail black or 

 dusky, faintly glossed with bluish; lores pale gray, darker next to 

 eyes; a spot above eye, auricu-lar region (the two confluent), suborbital 

 region, malar region, entire under parts, and patch on each side of 

 rump pure white; axillars and under wing-coverts pale gray, the lat- 

 ter becoming white on edge of wing; bill black; iris brown; legs and 

 feet dark brownish (in 'dried skins); length (skins), 122-125 (123.6); 

 wing, 122-125 (123-5); tail, 50-51 (50.5); exposed culmen, 6; width 



«The yoimg of T. t. lepida and T. t. brachyptera, only, seen; these do not differ in 

 coloration* 



