BIRDS OE' i^'orTh And middle America. VlS 



JCEY TO THE SPECIES AND SUBSPECIES OF POLIOPTILA. 



. Tail rounded or slightly graduated, the lateral retrices more than six-sevenths as 



long as middle pair; rectrices broader. 

 h. Outermost rectrix with more than terminal half white, 

 c. Head with more or less of black. 

 d. Black of head confined to a narrow U-shaped mark, extending across fore- 

 head and along sides of crown. 



e. Forehead and crown within U-shaped black mark bluish gray, not dis- 

 tinctly glossed. {Polioptila cserulea.) 

 f. Paler, the under parts white, or grayish white, shaded with pale bluish 

 gray on sides. 

 g. Larger (male averaging, wing more than 49, tail more than 50, tarsus 

 more than 17). 

 h. Black at base of lateral rectrix more restricted, usually concealed 

 by under tail-coverts; bluish gray of upper parts slightly clearer 

 and bluer; averaging, wing 52.1, tail 50.3, exposed culmen 9.9, 

 tarsus 17.2. (Eastern United States, south in winter to Baha- 

 mas, Cuba, and Guatemala. ) 



Polioptila cserulea cserulea, adult male (p. 716) 

 hh. Black at base of lateral rectrix, more extended, showing beyond 

 longest under tail-coverts; bluish gray of upper parts slightly 

 duller; adult male averaging, wing 49.9, tail 51.7, exposed cul- 

 men 10.2, tarsus 17.3. (Southwestern United States; western 

 Mexico in winter. ) .Polioptila cserulea bbsoura, adult male (p. 720) 

 gg. Smaller, except bill (male averaging, wing 47.5, tail 46.5, exposed 

 culmen 10.3, tarsus 16.3). (Southeastern Mexico to Guatemala.) 

 Polioptila caerulea mexicana, adult male (p. 722) 

 ff. Darker, the under parts light bluish gray, only the abdomen, anal 

 region and under tail-coverts white. (Bahamas; Cozumel Island 

 and adjacent coast of Yucatan. ) 



Polioptila cserulea csesiogastra, adult male (p. 723) 

 ee. Forehead and crown, within the U-shaped black mark, blackish slate, 

 distinctly glossed with greenish blue. (States of Oaxaca and Chia- 

 pas, southeastern Mexico.) Polioptila nelsoui, adult male (p. 724) 



dd. Black of head covering at least greater part of pileum.. 

 e. Lores at least partly white. 

 /. Superciliary region black (sometimes a white spot or streak above pos- 

 terior angle of eye, but this, if present, not confluent with white of 

 lores). 

 g. Lores entirely white; larger (wing averaging 49, tail 52.6). (Oaxaca 



to Guatemala. ) Polioptila albiloris, adult male (p. 725) 



gg. Lores not entirely white (a black line crossing from rictus to ante- 

 rior angle of eye); smaller (wing averaging 47.5, tail 46.8). 

 (Western Nicaragua and Costa Eica. ) 



Polioptila bairdi, adult male (p. 726) 

 ff. Superciliary region white (no black on lores). 



g. Larger (wing averaging 49, tail 43); back, etc., paler gray, under 

 parts more purely white, and tertials edged with white. ( Veragua 

 to Province of Santa Marta, Colombia. ) 



Polioptila bilineata, adult male (p. 726) 

 gg. Smaller (wing averaging 46.6, tail 39.7); back, etc., darker gray, 

 under parts strongly shaded with gray, and tertials edged with 

 pale gray. (Isthmus of Panama to Guatemala. ) 



Polioptila superciliaria superciliaris, adult male (p. 727) 



