I48 BIRDS OF THE REPUBLIC OF PANAMA PART 4 



York to West Virginia, and farther west from northern Michigan to 

 northern Minnesota. It winters from Mexico to northern Argentina. 



As on its northern breeding grounds, in Panama this is the most 

 arboreal of the spotted woodland thrushes. It is a regular visitor to 

 fruiting trees and bushes, and also sallies after insects. Willis (Liv- 

 ing Bird, 1966, p. 201-203) on Barro Colorado Island found that it 

 descends to the ground to follow swarms of army ants, pecking at the 

 insects flushed by the ants, and usually driving away Gray-cheeked 

 Thrushes and Veeries, but foraging only in niches not occupied by 

 resident species. Willis noted that when following army ants in No- 

 vember, Swainson's Thrushes would occasionally deliver fragments of 

 song, in addition to call notes. Skutch (A Naturalist in Costa Rica, 

 1971, p. 103) found them singing in Costa Rica from March to early 

 May. In Panama, Ridgely (in litt.) has heard in March and April "a 

 full whisper song similar to what one hears on migration in eastern 

 U.S." 



An interesting example of how rapidly these birds can put on weight 

 to increase the fat supply needed for migration is recorded by Leek 

 (Bird-Banding, 1975, p. 201), who netted a Swainson's Thrush at the 

 Volcan de Chiriqui Field Station of the Florida Audubon Society on 

 April 28, 1968, when it weighed 25 g, and retrapped it there 6 days 

 later, on May 4, when its weight was 31.6 g. 



CATHARUS MINIMUS MINIMUS (Lafresnaye) : Gray-cheeked Thrush; 



Zorzal Carigris 



Turdus minimus Lafresnaye, Rev. Zool., vol. II, no. 1, January, 1848, p. 5. (Bogota, 

 Colombia.) 



Medium size; upper surface dull olive; upper breast streaked irreg- 

 ularly with dusky, rest of undersurface white. 



Description. — Length 157-187 mm. Sexes alike; upper surface from 

 crown to back, olive to grayish olive; tail somewhat browner; side of 

 head grayish olive; no distinct eye-ring; ear region streaked narrowly 

 with dull white; side of jaw buffy white; undersurfaces of body white, 

 with upper breast washed with pale buff; sides of throat to upper breast 

 pale buff streaked irregularly with dusky; rest of undersurface white, 

 with the sides dull gray; underwing coverts dull gray, edged lightly 

 with white. 



In a male collected at Independence, Kansas, May 6, 1905, the iris 

 was brown, maxilla and tip of mandible black, rest of the bill dull yel- 

 low; tarsus dull brown. 



Measurements. — Males (10 from Alaska to Newfoundland), wing 



