216 BULLETIN 16 7, UNITED STATES NATIONAL MUSEUM 



occasions I have seen from the railroad, while passing through the 

 country between Casa Grande and Bowie stations, flocks of at least 

 fifty birds of this species, evidently migrating and closely associated 

 together. This was in the early part of September, 1882, and as 

 the train was going very slowly, and I was close to the birds, and 

 had become very familiar with them in life about Riverside in the 

 months just preceding, I could be very certain of my identification." 



DISTRIBUTION 



Range. — Southwestern United States, Central America, and north- 

 ern South America. 



The range of the zone-tailed hawk is very poorly understood. It 

 breeds north to Arizona (Big Sandy Creek, Prescott, Salt River, and 

 Paradise) ; southwestern New Mexico (Gila River and Tyrone) ; and 

 southern Texas (Guadaloupe Mountains, Davis Mountains, Devils 

 River, Fredericksburg, and Comal County). Most of the eggs that 

 have been collected have, in fact, been taken in the Southwestern 

 United States. 



From this northern part of the range the species occurs south 

 through Lower California, the mainland of Mexico, and other Cen- 

 tral American countries to Dutch Guiana (Surinam) ; British Guiana 

 (upper Pomeroon River) ; Venezuela (La Guaira and Macuto) ; Co- 

 lombia (Bonda and Mamatoco) ; Panama (Pearl Islands) ; and the 

 coast of Peru (Griscom, 1932). The southern part of this range is 

 occupied chiefly by a doubtfully distinct race {B. a. dbhrematus) .^ but 

 true dlbonotatus apparently breeds south as far as eastern Panama 

 (Perme), where a specimen was taken in the tropical lowlands on 

 August 7, 1929. 



Over nmch of its range it would appear that the zone-tailed hawk 

 is more or less resident, but during the winter season most individuals 

 withdraw from the United States, and in some Central American 

 localities (as Costa Rica) the species is known chiefly as a rare 

 migrant. 



Egg dates. — Arizona and Texas to Central America: 14 records, 

 February 2 to June 7; 7 records, April 13 to May 21. 



BUTEO ALBICAUDATUS HYPOSPODIUS Gurney 



SENNETT'S WHITE-TAILED HAWK 



HABITS 



The northern representative of this South American species ex- 

 tends its range into the United States only in the open and prairie 

 regions of southern Texas. George B. Sennett (1878) and Dr. James 

 C. Merrill (1879) were the first to record this handsome hawk as a 

 breeding bird in Texas. Both discoveries were made in 1878 near 



