BIRDft OF NORTH AND MIDDLE AMERICA. 729 



Adult female. — Length (skin), 106; wing, 47.5; tail, 43; exposed 

 cnlmen, 12.5; tarsus, 16.5; middle toe, 9.5. 

 Highlands of Costa Rica (Cartago). 



Polioptila supercilmris magna Ridgway, Proc. Biol. Soc. Wash., xvi, Sept. 30, 

 1903, 110 (Cartago, Costa Rica; coll. U. S. Nat. "Slu?.). 



POLIOPTILA ALBIVENTRIS Lawrence. 

 YUCATAN GNATCATCHER. 



Similar to P. nigriceps^ but smaller; gray of upper parts slightly 

 paler; under parts more pureW white, with gray tinge to chest and sides 

 much less distinct (the former sometimes quite wanting), and with 

 much more white on lateral rectrices; adult female with a narrow super- 

 ciliar}^ stripe of white." 



Adult male.— hength. (skins), lUO-lll (105.2); wing, 43-46 (45.3); 

 tail, 45-50 (48.2); exposed culmen, 11-12(11.4); tarsus, 16.5-18 (17.6); 

 middle toe, 8.5-9 (8.8).* 



Adult female. — Length (skin), 108; wing, 44; tail, 48; exposed cul- 

 men, 12; tarsus, 18.5; middle toe, 9.*' 



Yucatan (Temax; Progreso). 



(?) Polioptila bilineata (not Cnlicivora bilineata Bonaparte?) Boucard, Proc. Zool. 



Soc. Lond., 1883, 439 (Progreso, Yucatan).— Salvix, Ibis, 1888, 246 (Cozu- 



mel I., Yucatan; crit. ). 

 Polioptila alhirentris Lawrence, Ann. N. Y. Acad. Sci., iii, no. 9, Dec, 1885, 273 



(Temax, Yucatan; coll. G. X. Lawrence). 

 Plolioptllal alfiiiriitrifi Ridgwav, Man. N. Am. Birds, 1887, 569. — Hellmayr, Tier- 



reich, 18 Lief., 1903, 24. 



POLIOPTILA NIGRICEPS Baird. 

 BAIRD'S GNATCATCHER. 



Adult male in spring and summer. — Entire pileum, including nape, 

 lores,*' and upper half (more or less) of auricular region, uniform 

 glossy blue-black; hindneck, back, scapulars, lesser and middle wing- 

 coverts, and rump, uniform bluish gray (between plumbeous and slate- 

 gray); wings (except lesser and middle coverts) dusk}^ brownish slate 



« In the adult male of this form there is sometimes an indication of a white super- 

 ciliary streak. 



'' Six specimens. 



<^One specimen. 



<^ Occasionally there is a narrow loral streak, or indication of one, possibly the 

 result of incomplete change from winter to sununer phnnage; a narrow white 

 orbital ring is also sometimes indicated, this being characteristic of the winter 

 plumage. 



