SJALIA. 581 



back, scapulars, etc.; wings (except coverts) and tail as in 

 adult ; beneath white, the feathers of breast, etc., very broadly 

 bordered with dark grayish or brownish; a whitish orbital 

 ring. J^(j(js .82 X -64. Hub. Eastern United States, north to 

 Nova Scotia, Ontario, Manitoba, etc., west to base of Rocky 

 Mountains ; Bermudas (resident). 



766. S. sialis (Linn.). Bluebird. 



c'. Breast, etc., light ochraceous-cinnamon, the sides of neck and (usually) 



malar region similar. 



lZ'. Above light greenish blue or cerulean-bluo (much as in S. arctica), 



the sexes differing as in S. sialis ; anal region ciunamonbufF; 



length G.40-7.10, wing (male) 4.05-4.20 (4.10), tail 2.70-2.95 



(2.79), culmen .47-.50 (.49), tarsus .S0-.85 (.82). Female: Wing 



3.90, tail 2.55. Hub. Highlands of Mexico, north to southern 



Arizona 766a. S. sialis azurea (B.iiRu). Azure Bluebird.' 



d''. Above rich cobali-blue, varying to ultramarine, like S. sialis; 

 otherwise resembling S. azurea. Male: "Wing 4.15—1.35 (4.25), 

 tail 2.80-3.00 (2.93), culmen .50, tarsus .62-.65 (.63). Female: 

 Wing 4.05-4.10, tail 2.70-2.80. Hab. Highlands of Guatemala 

 and Honduras. 



S. sialis guatemalce Eidgw. Guatemala Bluebird.' 

 v. Throat and belly blue. 



Adult male : Above rich smalt-blue (varying to ultramarine), the back 

 usualh' with more or less of chestnut (sometimes entirely chestnut, 

 rarely entirely blue") ; lower parts lighter and duller blue, the breast 

 and sides deep cinnamon-chestnut. (Colors duller and more suf- 

 fused in winter.) Length 6.50-7.12, wing 3.95^.45 (4.19), tail 2.62- 

 3.05 (2.84), culmen .45-.50 (.43), tarsus .80-.90 (.82). Adult female: 

 Head, neck, and upper parts dull gray, paler on throat, browner on 

 back ; rump, upper tail-coverts, and tail bright blue, the outer web 

 of lateral tail-feather whitish ; wings dull blue ; breast and sides 

 dull light cinnamon ; bellj- dull grayish ; wing about 4.00, tail 2.50. 

 Youny: Not alwaj-s distinguishable with certainty from correspond- 

 ing stage of S. sialis, except by slenderer bill ; usually darker, how- 

 ever, especially on lower parts, the throat dull grayish and sides 

 tinged with dull dark brown. Eijgs .81 X -64. Hab. Western 

 United States, north to British Columbia, east to Rocky Moun- 

 tains, south over table-lands of Mexico. 

 (100.) 767. S. mexicana Swains. Western Bluebird. 



' Swainson's Sialin aziircn, usually quoted for this form, is a complete nomrn nndnm. The name was first 

 coupled with a description by Professor Baird (Review Am. B. i. July, 1S64, G2), who is thereforo to bo quoted 

 aa itj authority. 



' S. tialit gualemnlir Rinr.w.. Pr. l". S. Nat. Mus. v. Juno 5. 1?S2, 1.3. 



' This variation is purely individual, and not at all dependent on locality, as supposed by Mr. Sekeoiiii 

 (Cat. B. Brit. Mus. v. 1881, pp. 331-333). 



