AUGUST, 1915. NOTES ON SOUTH AMERICAN BIRDS CORY. 311 



A REVISION OF THE SPARROW HAWKS (GENUS CERCHNEIS) 

 OF SOUTH AMERICA AND ADJACENT ISLANDS 



In describing the supposed new subspecies belonging to this genus 

 in the present and in a previous paper,* the writer examined about 200 

 specimens from South America and adjacent islands, including the type 

 specimens of all the described forms except that of C, s. isabellina and 

 C. s. australis (gracilis Swainson). The study of this large series seems 

 to show: 



1. That the extent of the rufous on the crown (when present) is 

 more or less variable with the age of the individual, but, while in birds 

 from North America and the West Indies it is present in the majority 

 and is rarely entirely absent even in specimens which are evidently 

 adult, in birds from South America it is absent in the majority of speci- 

 mens and when present seems to be much more restricted in extent, 

 more than seventy-five per cent, of the series of males from South Ameri- 

 ca having no rufous on the crown and in a number of others having it 

 merely indicated by a slight trace. Very few males have a well marked 

 crown patch and at most it is apparently restricted to the basal half. 

 The material available is not sufficient to decide to what extent a rufous 

 patch is present in the very young of these forms. 



2. That no dependable correlation exists in the extent of the rufous 

 crown patch and the black banding of the back. Very young birds 

 apparently always have the back heavily banded, but in those which I 

 have examined the amount of rufous on the crown is very variable, one 

 young male from Curacao in its first plumage showing merely a trace of 

 rufous. Some apparently adult males have considerable rufous on the 

 crown and almost the entire back banded with black, while others from 

 the same region have about the same amount of rufous on the crown and 

 the back practically immaculate. Six apparently adult males from the 

 Rio Branco region (northern Brazil) have clear gray crowns, but three 

 of them have the back considerably banded and three have it almost 

 immaculate. Two specimens from the same region show a small rufous 

 patch on the crown; one of these has a few small bands on the lower back, 

 while in the other the back is nearly immaculate. While the females 

 from the same locality have the markings of the upper parts practically 

 identical, two have a rufous crown patch and in two it is absent. 



3. That the banding of the back apparently varies with age in indi- 

 viduals, but to what extent remains to be determined. In young males 

 the whole back is usually heavily banded, while in adults the upper back 

 at least is nearly or quite immaculate. 



* Field Mus. Nat. Hist. Pub., Ornith. Series, I, No. 8, 1915, pp. 293-302. 



