210 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I50 



Zone, December 18, 1910, and another obtained near Pacora Novem- 

 ber 28, 1958. The main flight seems to pass along the Pacific slope 

 and the central mountains from Darien to Chiriqui. In 1952 I saw 

 a flock at El Uracillo, Code, on the upper Rio Indio, but did not note 

 them at the mouth of the river on the Caribbean coast. There is no 

 present record for Bocas del Toro, nor for Herrera or Los Santos, 

 I have seen them on Taboga and Taboguilla, but not in the Pearl 

 Islands. 



The great flocks of these migrant hawks constitute one of the 

 notable sights for the ornithologist in this part of the world. While 

 other species, principally the broad-winged hawk and turkey vulture, 

 with scattered ospreys, marsh hawks and peregrine falcons may 

 join, half at least of these migrants are the present species. At times 

 they are seen in an endless line that moves high across the sky, until 

 one tires of watching. Or the birds may pass rapidly in groups of a 

 hundred to several thousand, that pause to circle in some rising air 

 thermal, and then move swiftly until they disappear. In full migra- 

 tion across the open savanna several such flocks may appear in view 

 simultaneously. On other days single birds and small groups pass 

 more leisurely at intervals. On various occasions when examining 

 some high-flying bird with binoculars I have seen large flocks of hawks 

 passing so high above the earth that they were not visible to the 

 unaided eye. 



The bands pause at night to sleep on some forested hill slope or 

 other spot where they will not be disturbed. While I have noted their 

 roosts in Panama only in trees, in Costa Rica and in El Salvador flocks 

 are recorded also as spending the night on the ground on open ridges 

 in the hills. They do not appear to stop for food, at least in the 

 isthmian part of their journey. Occasionally one or two alight on 

 the ground in the savannas, or on a rock on an open hillside, and some- 

 times small flocks may pass low overhead, but ordinarily they move far 

 beyond gunshot above the earth. For this reason few persons recog- 

 nize that they are hawks, and those who see them ordinarily call them 

 iroles or pdjaros del norte. The Cuna Indians call the moon that 

 approximates our month of September kigini or hawk, because of 

 the regularity with which these annual flights appear. The local name 

 irol applies to this species in the main, though the great mixed flocks 

 of Swainson's hawk and broadwings usually are called iroles with- 

 out understanding that two kinds are concerned. 



Like the turkey vultures these hawk flights move mainly by sailing 

 with set wings, propelled by favoring air currents, I recall one es- 

 pecially interesting flight seen in the latter part of March over the 



