346 Mr. W. L. Sclater on the [Ibis, 



This species has a rufous and a plumbeous phase ; examples 

 from Bahia show both extreme and intermediate stages of 

 the phases, but all retain some traces of the rufous on the 

 throat and chest. Birds from Rio Janeiro are all more or 

 less in the rufous phase, while two from Parana State and 

 Paraguay are in the plumbeous phase. 



Distribution. The series in the British Museum show a 

 range from Bahia in eastern Brazil south to Paraguay. It 

 does not appear to extend into the basin of the Amazon. 



Micrastnr rnficoUis gilvicollis. 



Sparvius gilvicollis Vieillot, N. Diet. d'Hist. Nat. x. 1817, 

 p. 323 : patr. ignot. [Cayenne, apud Hellmayr, Nov. Zool. 

 1908, p. 290 ; 1910, p. 410.] 



Nisus concentricus Lesson, Traite, 1831, p. 60 : Cayenne. 



Micrastur pelzelni Ridgway, Proc. Acad, Pliilad. 1875, 

 p. 494 : Sarayacu, Peruvian Amazons. 



This form seems never to have but the one plumbeous 

 phase. 



Distribution. Guiana and the Amazon valley from Para 

 to the eastern slopes of the Andes. 



Micrastur ruficoUis guerilla. 



Micrastur guerilla Cassin, Proc. Acad. Philad. 1848, 

 p. 87 : Jalapa, Mexico. 



Micrastur interstes Bangs, Auk, xxiv. 1907, p. 289 : 

 Costa Rica. 



The rufous and plumbeous phases in this subspecies are 

 much less differentiated than in M. r. ruficoUis. 



Distribution. From Vera Cruz State of Mexico south to 

 western Ecuador, whence there are examples in the British 

 Museum from Nanegal, 4000 feet, on the western slopes of 

 Pinchincha, 10 leagues from Quito, and from the Balzar 

 Mountains in the province of the same name in western 

 Ecuador. 



I have not examined the type of Micrastur interstes, but 

 I am quite unable to distinguish examples from Costa Rica 

 or southwards from those from Mexico. 



