BIRDS OF NORTH AND MIDDLE AMERICA 217 



gg. Size smaller, wings, cf under 250 mm., 9 under 270 mm. 

 (eastern, central, and southern Mexico), 



B. nitidus plagiatus, ad. (p. 359) 



dd. Underparts whitish streaked or spotted with dark brownish (young). 



e. Top of head whitish narrowly streaked with fuscous-black, in sharp 



contrast to the dark back. 



/. Underj^arts, and to a lesser extent crown, with a distinct pale 



cinnamomeous wash (southwestern Costa Rica to northern 



Columbia) B. nitidus blakei, juv. (p. 367) 



ff. Underparts and crown whitish or buffy whitish, not distinctly 

 washed with pale cinnamomeous. 

 g. Rectrices with the pale interspaces dusky hair brown on outer 

 webs of all and on inner webs of median rectrix as well. 



B. nitidus nitidus, juv. (extralimital) 

 gg. Rectrices with the pale interspaces whitish. 



B. nitidus nitidus, imm. (extralimital) " 

 ee. Top of head_^dark[^like]the rest of;;the upperparts. 



B. nitidus plagiatus, juv. (p. 360)'' 



B. nitidus micrus, juv. (p. 365) 



B. nitidus maximus, juv. (p. 362) 



bb. Longest primary exceeding distal secondary by very nearly one-third to 



more than one-third the length of the wing ("subgenus Buteo") 



c. Tail more than half as long as wing, tarsus much less than half as long as 

 tail. 

 d. Three outer primaries distinctly emarginate or sinuate on their inner 

 webs. 

 e. Size larger; wing always over 360 mm. (either sex). 

 /. Culmen from cere (chord) over 26 mm. in male, over 30 mm. in 

 female. 

 g. Entire bird nearly uniform sooty brown (Galdpagos Islands). 



B. galapagoensis, ad. (p. 272) 

 gg. Underparts ochraceous-buff splotched and streaked with dark 



brown B, galapagoensis, juv. (p. 272) 



ff. Culmen from cere (chord) 25 mm. or less (either sex) (northern 

 North America south to Chile in winter). 

 g. Entire body and head uniform dark brown. 



B. swainsoni, ad., dark phase (p. 296) 



gg. Underparts buffy or rufescent more or less marked with dark 



brown. 



h. Underparts with some dark brown or blackish. 



i. Underparts dark brown or blackish with some whitish spots 



and streaks B. swainsoni, juv., dark phase (p. 297) 



12 The immature plumage of Buteo nitidus blakei is unknown to me. 



" I know of no trenchant characters by which young birds of these three forms 

 may be separated. The ju venal plumage appears to be worn for a year in these 

 races and to fade considerably during that time so that a year-old (immature) 

 bird looks much paler, more earth brown, less fuscous, than a bird of the year. 

 The fact that these three forms, with upperparts unbarred or almost so in the 

 adult plumage, lack a true immature plumage may be looked upon as suggesting 

 that they form one species and that nitida and blakei (and the Bolivian race, 

 ■pallida), with barred upperparts in the adult plumage and with a definite (at 

 least in nitida) immature plumage, may form another species rather than that all 

 are conspecific. I still incline, however, to the latter view. 



