366 BIRDS OF THE REPUBLIC OF PANAMA PART 4 



sometimes chestnut feathers on yellow undersurface; tail feathers 

 black, edged green. 



Measurements. — Males (10 from North America, taken in April to 

 June), wing 74.5-82.0 (78.7), tail 66.3-71.3 (69.2), culmen from base 

 16.1-18.2 (16.9), tarsus 19.6-21.9 (20.8) mm. 



Females (10 from North America, taken in April to July), wing 

 74.0-78.0 (75.9), tail 62.6-69.0 (66.4), culmen from base 15.5-17.7 

 (16.6), tarsus 19.3-22.1 (20.5) mm. 



Migrant and winter visitor from the north, breeding in eastern 

 United States and southeastern Canada. Common in the lowlands of 

 both slopes (less so on the Pacific slope of the western provinces), 

 where it has been recorded from late July until mid-April; occasionally 

 it is found on migration in the highlands up to 1650 m (Ridgely, 1976, 

 p. 309) . It occurs in light woodlands and open areas with trees. W. W. 

 Brown, Jr. (Thayer and Bangs, Bull. Mus. Comp. Zool., vol. 46, 1905, 

 p. 157) collected an adult male on Saboga Island, in the Perlas Archi- 

 pelago, on April 13, 1904, and Eisenmann observed an immature male 

 (with black throat) on Isla Coiba on October 9, 1965, but it is not other- 

 wise recorded from any of the islands off either coast. It winters from 

 southern Mexico to northern Colombia and Venezuela. 



Most Orchard Orioles arrive in Panama in August and leave by mid- 

 March. An indication of its abundance as a migrant in central Panama 

 is Lof tin's report (in litt. to Wetmore) that he banded 68 on October 

 18-19, 1963, 4.8 km east of Panama City. During the winter, it gathers 

 in roosts that may be used in successive years; one in a tree in front of 

 the Ancon Police Station in the Canal Zone held at least 100 birds when 

 I saw it in February 1952 and December 1955. Another, near the old 

 Tocumen airport, had 300-400 in December 1973-January 1974; these 

 birds seem to have shifted to the La Siesta Hotel. Eisenmann notes 

 that most of the Orchard Orioles he saw in central Panama during the 

 northern winter were adult male, in chestnut plumage. 



When in Panama, the Orchard Oriole feeds to some extent on nectar, 

 particularly that of the tree Erythrina fusca. 



Morton (Ann. Missouri Bot. Gard. 66, 1979, pp. 482-489) speculates 

 that the identical color of the adult male Orchard Oriole's body plum- 

 age and the floral parts surrounding the nectar of Erythrina fusca in- 

 dicates a coevolved relationship. He notes that adult male Orchard 

 Orioles exclude females and immatures from these trees when they are 

 in flower, which is at the time the orioles are most abundant in Panama. 

 The Orchard Oriole is the only species that opens Erythrina flowers 

 "correctly," thereby getting pollen on its chest. The correctly opened 



