224 



BIRDS OF THE REPUBLIC OF PANAMA PART 4 



tail 42.1-48.1 (45.9), oilmen from base 10.1-11.9 (10.9), tarsus 12.8- 

 16.7 (15.6) mm. 



Females (10 from Panama), wing 61.0-69.2 (64.6), tail 38.1-45.5 

 (43.2), culmen from base 9.9-11.7 ( 10.6) , tarsus 13.3-16.9 (15.4) mm. 



Migrant from the north, and winter resident. Common in foothills 

 and highlands of Chiriqui and Veraguas, rarer in lowlands of western 

 and central Panama. The farthest east in Panama from which this 

 species has been reported is in the Bayano River basin, on January 10, 

 1976 (J. J. Pujals, to Eisenmann). The Philadelphia Vireo is found 

 in Panama from October to mid or late April; usually it inhabits wood- 

 lands, where it often travels with mixed flocks of North American 

 migrants especially warblers, but I have also found it in mangrove 

 swamps on islands off the Pacific Coast. The highest elevation at which 

 it has been collected is 1620 m, at Lerida, Chiriqui, by Monniche (Blake, 

 Fieldiana: Zool., vol. 36, no. 5, 1958, p. 554) and at Quiel, near Bo- 

 quete, by Benson, and there are numerous records from elsewhere in 

 the highlands of Chiriqui and Veraguas. I have collected Philadelphia 

 Vireos in Chiriqui at elevations from 1260 m at El Volcan and Santa 

 Clara, to Concepcion, 240 m, down to Las Lajas, Puerto Armuelles, 

 and Punta Balsa, at or near sea level, and Isla Parida offshore. 



In the Veragus highlands, Arce collected the Philadelphia Vireo at 

 Chitra (Salvin and Godman, Biol. Centr.-Amer., Aves, vol. 1 (pt. 14), 

 1881, p. 191) and Ridgely (in lift.) with F. Gary Stiles reports a "flock 

 of at least 30 in woods along river below Santa Fe [1200 m.] in part as- 

 sembled by Stiles' pygmy-owl hooting" on January 6, 1974. My only 

 encounters with the Philadelphia Vireo in Veraguas have, in contrast, 

 been on islands off the Pacific Coast— Cebaco, Gobernadora, Afuerita, 

 and Coiba. 



On the western side of the Azuero Peninsula, Aldrich and Bole 

 (Scient. Publ. Cleveland Mus. Nat. Hist., vol. 7, 1937, p. 118) found 

 the Philadelphia Vireo "rather common in mixed flocks of arboreal 

 North American migrants." Specimens at the Smithsonian from other 

 provinces include birds from Almirante, Bocas del Toro; Santa Maria, 

 Herrera; Pedasi, Los Santos; and Tigre, at the head of the Rio Guabal, 

 Code. Ridgely (1976, p. 285-286) mentions some recent reports by 

 Eugene S. Morton of the Philadelphia Vireo in the Canal Zone: "one 

 collected at Albrook Air Force Base on February 19, 1971; one seen 

 at Madden Lake Scout Camp on February 26, 1971; one collected at 

 Gatun Dam on April 4, 1971." 



Like many insectivorous migrants from North America, the Phila- 

 delphia Vireo becomes more sociable out of the nesting season and more 



