FAMILY ACCIPITRIDAE 21/ 



on lower surface averaging broader and darker brown; light bars 

 whiter ; light tail bands grayer, less rufous. 



Measurements. — Males (7 specimens), wing 210-222 (215), tail 

 142-161 (150), culmen from cere 18.2-20.3 (19.0, average of 6), 

 tarsus 62.1-67.2 (64.1) mm. 



Females (2 specimens), wing 226-234 (230), tail 156-160 (158), 

 culmen from cere 19.5-19.8 (19.6), tarsus 66.0-69.1 (67.5) mm. 



Resident. Found in the Archipielago de las Perlas, where it is 

 recorded from Isla del Rey, Isla Caiias, Isla San Jose, and Isla Pedro 

 Gonzalez. 



The birds were fairly common on Isla San Jose in 1944, but on 

 visits to the other islands on which they are reported I have found 

 them in smaller numbers. Like the races of the mainland, they range 

 around clearings in inhabited areas, and where forests persist rest in 

 the better-lighted upper branches in the tallest trees. 



At times I saw yellow-green vireos scolding them. As I have not 

 observed this regularly elsewhere, it is an indication that this race 

 may be more predatory on the nests of neighbor birds than seems to 

 be the case on the mainland, where the lizards and large insects that 

 are its usual food are more abundant. 



B. m. alius, in larger size and grayer tail bands, shows approach to 

 the subspecies insidiatrix of the northern coast of Colombia. 



LEUCOPTERNIS ALBICOLLIS COSTARICENSIS Sclater: White Hawk; 



Gavilan Blanco 

 Figure 43 



Leucopternis ghieshrcghti costaricensis W. L. Sclater, Bull. Brit. Orn. Club, vol. 

 39, April 9, 1919, p. 16. ("Carillo" = Carrillo, Costa Rica.) 



Of medium size ; white, with black-tipped wings, and black-banded 

 tail. 



Description. — Length 470 to 510 mm. Adult, pure white, with 

 primaries and secondaries black, the latter tipped broadly with white ; 

 a broad black subterminal bar on the tail ; some black mottling or 

 streaking on the wing coverts and tertials ; under surface of wing 

 mainly white, with ends of flight feathers black, barred above the 

 tips with light gray. 



Immature, with narrow shaft lines of black on the crown and more 

 black in the wings. 



In two adult males I recorded the following colors : Iris brown ; 

 bare skin around eye greenish slate ; tip of bill dark neutral gray to 

 black ; base clear light gray ; cere greenish gray ; tarsus and toes dull 

 light yellow, with the scutes on the inner side of the front of the 

 tarsus tinged centrally with pale neutral gray ; claws black. 



