112 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



form with which it is identified. An immature male from Rio Negro, 

 Uruguay, secured February 15, is also slightly intermediate in its 

 characters. 



Hellmayr '•'^ has proposed to replace the subspecific name yucKerani 

 by su'perciliaris from Sparvius superciliaris Vieillot^* based on the 

 esparvero pardo ceja hlanca of Azara. Azara, however, says in the 

 beginning of his description that the feathers of the head and nape 

 in his bird were pointed, while the remaining plumes of the dorsal 

 surface had rounded ends, a character not to be found in Rupomis^ 

 so that he must have had some other hawk in mind. Though the 

 remainder of the description may fit the immature stages of the 

 present bird, this first statement must identify the bird described 

 as one of some other genus. It is curious that Azara's Esparvero 

 indaye, which is undoubtedly a Ruporivis^ was not given a name by 

 those who republished his descriptions. 



This small hawk was common in open wooded regions of the 

 Chaco in northern Argentina and Paraguay, and was observed in 

 less abundance in Uruguay. It frequented the borders of groves 

 where it might perch in the shade or the open as desired. The 

 caranchillo, as the bird was called, was fearless often to a point of 

 stupidity, and was seldom alarmed even by a gunshot fired close at 

 hand. In regions where it was common it came almost invariably 

 when I was "squeaking" to draw warier denizens of the thickets 

 from cover, and perched near at hand with jerking tail while it 

 peered about to locate the sound. Though most other birds were 

 little afraid the squalling calls of the hawk caused some to remain 

 partly concealed, and even frightened shyer ones from appearing 

 at all, so that at times I found Rupornis considerable of a nuisance. 

 Toward the end of August the mating season seemed near as the 

 hawks became very noisy, and screaming shrilly, often turned in 

 short circles two hundred meters in the air, while others squealed in 

 answer from the tree tops below. 



An adult female taken July 26 had the soft parts colored as fol- 

 lows: Tip of bill dull black, base clear green-blue gray, becoming 

 deep colonial buff on rami of mandible; cere primuline yellow; iris 

 massicot yellow ; tarsus and toes honey yellow ; claws black. 



These hawks were recorded as follows: Resistencia, Chaco, July 

 9 and 10; Las Palmas, Chaco, July 13 to 31; Riaqho Pilaga, For- 

 mosa, August 7 to 21; Formosa, Formosa, August 23 and 24; Puerto 

 Pinasco, Paraguay, September 3 to 25 (observed west to a point 200 

 kilometers from the Rio Paraguay) ; San Vicente, Uruguay, Janu- 

 ary 31, 1921 (two seen) ; Rio Negro, Uruguay, February 15 to 18. 



The pelvic powder downs in these hawks are well developed. 



s^Nov. Zool., vol. 28, 1921, p. 183. 



" Nouy Diet. Hist. Nat., vol. 10. 1817, p. 328. 



