450 Annals of the Carnegie Museum. 



men and thighs spotted with sooty- 

 brown. Buteo plalypterus, juv. 

 jj. Larger (wing, 400); throat and abdo- 

 men streaked, breast unmarked ; 

 thighs brokenly barred. 



Buteo borealis costaricensis, juv. 

 ff. Under tail-coverts streaked or barred. 

 g. Tarsi shorter (75 to 90). 



h. Tail (dorsal view) sooty-brown, with indistinct 

 bars of darker sooty; under parts heavily 

 obscured with sooty-brown (tarsi, 75). 



Buteo swainsoni, juv. 

 kh. Tail buff-white, with about six black bars (tarsi, 

 90); deep ochraceous below, streaked with 

 black, thighs barred with black. 



Urubitinga anthracina, juv. 

 gg. Tarsi longer (no mm.); under parts deep ochre, 

 streaked and spotted with dark brown ; upper 

 tail-coverts buff. 

 h. Markings on breast heavier. 



Urubitinga urubitinga ridgwayi, juv. 

 hh. Markings on chest narrower. 



Urubitinga urubitinga, juv. 

 cc. Tail less than one-half the length of wing. 



d. More than half of basal portion of tail white or grayish-white (ven- 

 tral surface) . 

 e. Shoulders and tertials largely chestnut-brown ; lower parts 

 white, finely barred on abdomen and thighs with dark 

 rufous. Buteo albicaudatus sennetti, adult. 



ee. Shoulders and tertials not chestnut-brown ; inner wing- coverts 

 white, strongly barred with dark brown ; lower parts white, 

 coarsely and brokenly barred on abdomen and thighs or else 

 nearly entire lower parts obscured by sooty-brown or blackish. 



Buteo albicaudatus sennetti, juv. 

 dd. Tail not largely white or grayish- white. 



e. Nearly entire upper and lower parts chestnut-brown ; primar- 

 ies, secondaries, and rectrices black ; a patch of black on 

 lower throat (young with dark spots and streaks on abdo- 

 men). Busarellus nigricollis. 

 ee. Slaty-black above, feathers narrowly margined with whitish ; 

 below whitish, broadly streaked with slaty-black. 



Ictinia plumbea, juv. 



124. Polyborus cheriway (Jacquin). 



Falco cheriway Jacquin, Beitrag, 1 784, 17, t. 4. 



Polyborus cheriway Cabanis, in Schomb. Reis. Guiana, III, 741. — Sharpe, Cat. 

 Birds Brit. Mus., I, 1874, 33. —Zeledon, An. Mus. Nac. de C. R., 1, 1887, 



