2l6 



BIRDS OF THE REPUBLIC OF PANAMA PART 4 



p. 194) banded Red-eyed Vireos at Almirante between April 8 and May 

 13. On most days no more than 6 were found in the nets, but on April 

 18-19, 10 birds were taken each day and on April 28-30 from 10 to 18 

 each day; after April 30 no more than 2 were netted each day. 



The large number of birds netted at Almirante has provided oppor- 

 tunities to study the amount of energy expended by migrants. It is not 

 known whether vireos reaching Panama in fall have flown nonstop 

 from the United States or have come from farther north in Central 

 America. Rogers and Odum (Wilson Bull., 1966, p. 421) found that 

 newly-arrived Red-eyed Vireos had depleted their fat reserves and 

 some were believed to have lost some of their fat-free weight as well. 

 In an earlier study, however, Rogers (Bird-Banding, 1965, p. 116) 

 collected a vireo killed in an October rainstorm at Almirante and esti- 

 mated that on the basis of its remaining available fat it could still have 

 flown another 658 km. A male I collected at La Jagua, Province of 

 Panama, on March 20, 1961, was packed with fat. 



While in Panama, Red-eyed Vireos include fruit in their diet; from 

 September to November 1968 Leek (Living Bird, 1971, p. 92) ob- 

 served them repeatedly visiting a tree with mistletoe berries. In spring 

 I have seen them moving through the trees with other migrant insecti- 

 vores. 



VIREO OLIVACEUS OLIVACEUS (Linnaeus) 



Muscicapa olivacea Linnaeus, 1766, Syst. Nat, ed. 12, 1, p. 327; based mainly on 

 "The red-Ey'd Fly-catcher, Muscicapa oculis rubris" of Catesby, 1731, Nat. Hist. 

 Carolina, 1, p. 54, pi. 54, lower fig. (North America [ = (South) Carolina].) 



Characters. — Olive-green of upper surface darker than caniviridis, 

 without grayish wash; pileum darker, mouse gray rather than olive- 

 gray; undersurface with yellowish wash in sides and flanks. 



Measurements. — Males (10 from northwest Canada and United 

 States, collected in May and June), wing 77.2-83.0 (80.6), tail 45.2- 

 57.2 (54.4), oilmen from base 12.3-14.7 (13.4), tarsus 17.1-19.1 

 (17.8) mm. 



Females (10 from northwest Canada and United States, collected in 

 May and June), wing 75.0-79.8 (77.1), tail 48.0-53.6 (51.1), oilmen 

 from base 13.0-14.5 ( 13.6) , tarsus 16.4-18.8 (17.7) mm. 



Migrant and possibly winter visitant from the north. As a transient, 

 Griscom (Bull., Mus. Comp. Zool., vol. 78, 1935, p. 364) called the 

 Red-eyed Vireo common throughout. It has been recorded at sea level, 

 on islands including Saboga, in the Pearl Islands (Thayer and Bangs, 

 Bull. Mus. Comp. Zool., vol. 46, 1905, p. 154), and on Taboga (speci- 



