FAMILY IIIRUNDINIDAE 



paper added when the site is in or near human habitation. In any lo- 

 cation they seem less gregarious than the Purple Martin, as the nest 

 sites occupied normally are separated, not close together. On Gatun 

 Lake, Canal Zone, pairs build regularly in the top of the metal chan- 

 nel markers. In the nesting period these martins are vigorous in attack- 

 ing hawks and other large predatory birds that attempt to perch on or 

 near their nesting trees. 



Eisenmann writes that the full extent of the nesting season in Pan- 

 ama still remains to be determined: pairs with eggs or nestlings have 

 been reported from March through early August, and he has seen pairs 

 seemingly on territory near a tree hole or building cranny in February. 

 On the San Bias coast and the nearby island of Mulatupo on Decem- 

 ber 1 and 2, 1962, he saw a few isolated pairs about nest sites, sug- 

 gesting that the nesting season may extend over much of the year, un- 

 less pairs guard nest sites out of the nesting period. 



The eggs are white, with from 2 to 5 recorded in the set. Size 

 ranges from 21.4-26.3 by 15.0-17.1 mm. (Meise in Schonwetter, 

 Handb. Ool., part 17, 1970, p. 193). A. Hartley (in Beebe, Hartley, 

 and Howes, Tropical Wildlife in British Guiana, vol. 1, 1917, pp. 328- 

 334), in an account of this species, recorded careful nest sanitation in 

 which the parents removed the excrement of the nestlings. Food, as 

 usual in this family, is composed of insects taken on the wing. Like 

 other swallows, they swoop regularly to the surface of open waters to 

 drink. Two collected by Burton (Bull. Brit. Orn. Club, 1975, p. 92) at 

 Pacora, Province of Panama, weighed 40 and 44 g. 



At El Real, Darien, on January 7, 1964, I saw a curious aggressive 

 reaction on the part of a Gray-breasted Martin that perched regularly 

 for hours each day in a high dead treetop opposite our house. One after- 

 noon, a skipper butterfly (Family Hesperiidae) , in its usual rapid, er- 

 ratic flight, darted about over the trees and houses. Its restless activity 

 seemed to irritate the martin, as whenever the insect rose into the open 

 air, the bird swooped at it and then returned to its perch. This con- 

 tinued until finally the martin hit the insect with its breast, a clearly 

 audible blow that knocked the skipper to the ground. There it lay for 

 a minute or two with spread wings, partly stunned, until presently it 

 rose, darted away, and disappeared. There was no indication that the 

 bird had tried to seize it. 



Eisenmann believes that some birds of this race from Mexico at 

 least occasionally winter or pass through Panama, as birds of northern 

 Mexico are known to be migratory and flocks of this species are some- 

 times seen when local birds are nesting. The southern race (domestica) 



