BIRDS OF NORTH AND MIDDLE AMERICA 131 



in two or more longitudinal series; middle toe about three-fourths as 

 long as tarsus; outer toe decidedly longer than inner toe, the latter 

 reaching beyond distal end of second phalanx of middle toe; hallux 

 about as long as inner toe, its claw longer than the digit; all the claws 

 long, slender, slightly curved, and acute, the middle one with inner 

 edge produced, except for terminal third, and broken by a few trans- 

 verse fissures; web between basal phalanges of outer and middle toe 

 barely obvious. 



Plumage and coloration. — Plumage full and, for the greater part, 

 blended, the feathers of the mantle, however, rather distinctly out- 

 lined ; loreal and rictal regions and mandibular rami nude, with a few 

 small bristles; chin with semiantrorse feathers with long slender bristle- 

 like tips. Adults plain slate color or brownish slate, becoming nearly 

 black on head, remiges, and tail, the last white at base and broadly 

 tipped with pale gray or grayish white; tail coverts white. Young 

 huffy (more or less deep) below, spotted and striped with dusky, 

 dusky above, the feathers margined and otherwise variegated with 

 buffy, the tail as in adults. 



Bangs. — Tropical and subtropical America, from Florida and Cuba 

 to Argentina and Peru. (Monotypic.) 



KEY TO THE SUBSPECIES OF ROSTRHAMUS SOCIABILIS 



a. Culmen from cere (chord) under 30 mm. 

 \b. Wing relatively short, usually under 340 mm. (Nicaragua to Argentina). 



R. s. sociabilis (p. 131) 

 &&. Wing relatively longer, over 340 mm. 



c. Culmen from cere (chord) 25 mm. or less in length (average 23.3 mm.) 



(Florida) R. g. plumbeus (p. 136) 



cc. Culmen from cere (chord) 25 mm. or more in length (average 25.2 mm.) 



(Cuba and Isle of Pines) R. s. levis (p. 139) 



aa. Culmen from cere (chord) 30 mm. or longer (e. Me.\ico).B. s. major (p. 138) 



ROSTRHAMUS SOCIABILIS SOCIABILIS (Vieillot) 



SotTTH American Snail Kite 



Adult male. — Entire head, back, wings, breast, abdomen, sides, 

 flanks, and thighs uniform slate or blackish slate color, becoming 

 nearly black on the remiges and rectrices (which latter are light tipped 

 as indicated below), and with a faint brownish mouse gray tone on the 

 upper wing coverts; upper and under tail coverts and base of tail 

 whitish; tips of rectrices whitish with a broad subterminal band of 

 mouse grayish drab; the lores and external rim on the eyelids entirely 

 nude and flame scarlet in color; bill mainly black; cere, gape, and 

 mandibular rami flame scarlet; iris carmine; tarsus and toes apricot 

 orange; claws black. 



839094—50 10 



