142 BULLETIN 50, UNITED STATES NATIONAL MUSEUM, 



SIALIA SIALIS SIALIS (Linnaeus). 

 BLUEBIRD. 



Adult male in spring and summer.— Vpper parts uniform bright blue, 

 varying in hue from sevres bhie" to smalt blue, the average hue 

 being between ultramarine and smalt, the shafts of remiges and rec- 

 trices black, and tips of remiges (especially primaries) dusky; sides of 

 head, including malar region (sometimes including also chin and sides 

 of upper throat) lighter and grayer blue; throat, chest, breast, sides, 

 and flanks, uniform didl cinnamon-rufous or cinnamon-chestnut; 

 abdomen, aiial region, and under tail-coverts, white, the last with 

 longer feathers tinged with pale grayish blue, the shorter (basal) ones 

 with pale cinnamon-rufous; axillars and under wing-coverts pale 

 grayish blue ; bill, legs, and feet, black ; iris, dark brown. 



Adult male in autumn and vmiter. — Similar to the spring and sum- 

 mer plumage, but blue of upper parts slightly duller, more or less 

 obscured on hirdiieck, back, and scapulars, by brownish tips to the 

 feathers, and cinnamon-rufous of chest, etc., more purplish or vina- 

 ceous in hue. 



Adult female. — Above l)luish gray, more or less tinged with light 

 grayish brown (especially in autumn and winter), passing into bright 

 blue (cerulean to azure) on rump, upper tail-coverts, and tail; wings 

 blue, the tertials and innermost greater coverts more or less distinctly 

 edged with pale brownish gray or whitish, the outermost primary 

 edged with white ; anterior and lateral under parts dull rufous-cinna- 

 mon or cinnamon-brown (paler in summer, deeper in fresh autumn 

 plumage), the chin and upper throat paler; abdomen, anal region, 

 and under tail-coverts white. 



Young male. — Pileum, hindneck, back, scapulars, rump, and lesser 

 and middle wing-coverts sooty grayish brown or brownish slate tinged 

 with sooty, the back and scapulars (sometimes rump also, but less 

 distinctly) streaked with whitish; middle wing-coverts with a small 

 terminal spot of whitish; greater wing-coverts, primaries, and rectrices 

 bright l)lue (as in the adult male) but tertials broadl}^ edged with 

 brown and margined terminally with pale gray or grayish white; 

 under parts white, the feathers of chest and sides edged or margined 

 with brown (most heavily on chest), producing a conspicuous 

 streaked or scpiamate appearance; a whitish orbital ring. 



Young female. — Similar to the young male, but blue of wings and 

 tail much duller, and dusky streaking or squamation of under parts 

 heavier and more extended. 



Adult maZe.— Length (skins), 148-173 (155); wing, 96.5-104.5 

 (100.1); tail, 59.5-68.5 (63.7); exposed culmen, 11-14 (12.3); tarsus, 

 19-21.5 (20.3); middle toe, 15-17.5 (16.2).^ 



aThis light greenish bhic (the characteristic color of S. s. fulva and S. arctica) is 

 very exceptional, however. 

 b Fifty-one specimens. 



