376 BIRDS OF THE REPUBLIC OF PANAMA PART 4 



tail 69.4-74.1 (71.5), culmen from base 18.1-19.9 (19.1), tarsus 21.7- 

 24.4 (22.9) mm. 



Females (10 from Panama), wing 87.0-95.0 (91.8), tail 63.7-75.6 

 (68.7), culmen from base 17.8-20.9 (18.9), tarsus 18.8-24.5 (22.5) 

 mm. 



Migrant and winter visitor from the north. Common throughout, 

 mostly in the lowlands, but in Chiriqui also reaches the highlands to 

 over 1800 m (Ridgely, 1976, p. 311) ; it has also been recorded on some 

 of the islands in the Pacific (Coiba I., Saboga L). The winter range 

 of the Northern Oriole extends to Colombia and northern Venezuela; 

 the first migrants occasionally arrive in Panama in late September and 

 also linger into May, but most are found between early October and 

 late April. Eisenmann (in litt.) reports late dates from the Canal Zone 

 of May 11 (Fort Davis Woods) May 19 (Barro Colorado I.) and May 

 27 ( Achiote Road, 1977, a year when N. G. Smith found many northern 

 migrants remaining exceptionally late). In my experience the spring 

 migration begins in the first week of February. As in North America, 

 the Northern Oriole here is found at the edges of woodland and in 

 open areas with trees. Individuals may spend several months at one 

 locality; 1 banded at Almirante, Bocas del Toro, on October 7, 1963, 

 was recaptured there January 29, 1964 (Loftin, Rogers, and Hicks, 

 Bird-Banding 1966, p. 43). 



When in Panama, Northern Orioles often feed in flowering trees, 

 where they take nectar as well as insects (Leek, Auk, 1974, pp. 162- 

 163). At certain rich food sources they may become territorial, as has 

 been reported from Costa Rica, where Schemske (Auk, 1975, p. 595) 

 saw 1 drive hummingbirds, wrens, warblers, tanagers, and other orioles 

 away from its section of a flowering tree. I have also seen a male 

 Northern Oriole repeatedly chase a female from his chosen roosting 

 spot. In another study in Costa Rica, Timken (Wilson Bull., 1970, pp. 

 184-188) found that Northern Orioles take some fruit, but mostly 

 insects, while in flowering or fruiting trees, and feed primarily in early 

 morning and late afternoon. In Panama I have seen them lean over to 

 probe the termite runs on the underside of tree branches. At dusk they 

 roost communally in trees that may be used year after year, sometimes 

 in association with Orchard Orioles (/. spurius) ; as they gather for the 

 night Northern Orioles sometimes give a few calls. Ridgely (in litt.) 

 has heard males give brief bouts of singing, sometimes in flight between 

 trees, in March and April. 



I have never seen a skin taken in Panama that showed any of the 

 characters of the western /. g. bullocki, but a female apparently of this 



