BIRDS OF NORTH AND MIDDLE AMERICA. 7 18 



KICY To TIIK SI'KC'IKS AND srHSl'IOflES OK Pol.h H'TII.A. 



a. Tail roundi-d or sli<,'litly t;ra<luiited, llie lateral ntriccs more than six-wvi'iillis as 

 Ioii<; a.s iniddk' pair; rt'cti'iccs broader. 

 I). < )iitermost rt'ctrix witli mure tliaii teriiiinal lialf white. 

 r. Head witli more or less of black. 



(/. Black of liead eonliiied to a narrow U-shaped mark, exteiiiiin<j; across fore- 

 head and aloiij; sides of crown. 



*'. i"'oreliead and crown within U-shapeil black mark liluish >rray, not dis- 

 tinctly <jlossed. (J'(di(jj)lil(i nirnlt'd.) 

 f. Paler, the nnder parts white, or <rrayisli white, shaded with pale bluish 

 gray on sides. 

 <j. Larger (male averaging, wing more than 4;t, tail more than oO, tarsus 

 more than 17). 

 /(. Black at base of lateral rectrix more restri(;ted, usually con<'ealed 

 by nnder 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 Tnited States, south in winter to Baha- 

 mas, Cuba, anil (luatemala.) 



Polioptila caerulea caerulea, adtilt male (p. 71(1) 

 hh. Black at base of lateral re<;trix, more extended, showing beyond 

 longest under tail-coverts; bhiish gray of ujjper parts slightly 

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

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

 ^lexico in winter. ) .Polioptila caerulea obscura, adult male (p. 720) 

 g<j. Smaller, except bill (male averaging, wing 47.5, tail 46.5, exposed 

 culmen 10.3, tarsus 16.3). (Southeastern ^lexico to (iuatemala. ) 

 Polioptila caerulea mexicana, adult male (p. 722) 

 ff. Darker, the under paits light bluish gray, oidy the abdomen, anal 

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

 and adjacent coast of Yucatan.) 



Polioptila caerulea caesiogastra, adult male (p. 723) 



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



distinctly glo.ssed with greenish blue. (Stktes of Oaxaca and Chia- 



l)as, southeastern jSIexico. ) Polioptila nelsoni, a<bi]*^ male (p. 724) 



(/'/. Black of head covering at least greater jvart of jiileum. 

 ('. Lores at least partly white. 

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

 terior angle of eye, lint this, if j)resent, not conHuent with white of 

 It )res ) . 

 tj. TiOres entirely white; larger ( wing averaging 49, tail 52.6). (Oaxaca 



to (inatemala.) Polioptila albiloris, a<hilt male (p. 725) 



fj(j. I.,ores not entirely white (a black line crossing from rictus to ante- 

 rior angle of eye); smaller (wing averaging 47.5, tail 46.S). 

 (Western Nicaragua and Costa Rica.) 



Polioptila bairdi, adult male (p. 726) 

 j'j. Superciliary r«'gion white (no black on lon-s). 



(J. Larger (wing avi'raging 49, tail 43); back, etc., paler gray, under 

 parts more purely whiti", and tertials eilged with white. (Veragua 

 to Province of Santa Marta, Colondiia. ) 



Polioptila bilineata, adult male (p. 726) 

 ij(j. Smaller (wing averaging 4().(), tail 39.7); back, etc., darker gray, 

 under j)arts strongly shaded with gray, and tertials edged with 

 pale gray. ( Isthnms of I'anama to (inatemala.) 



Polioptila superciliaris superciliaris, adult male (p. 727) 



