FAMILY TURDIDAE 



145 



Description. — Length 148-185 mm. Sexes alike; upper surface from 

 crown to lower back uniform olive to sepia, upper tail coverts slightly 

 brighter; wings and tail olive to sepia, with basal third of all but outer- 

 most primary and innermost secondary lighter (more distinctly on un- 

 dersurface of wing) ; distinct buffy white streak at lores and eye-ring; 

 side of face like back; throat buffy white, streaked with dark brown on 

 sides; upper breast washed with pale buff and spotted with dark brown; 

 rest of undersurface white with sides color of back; underwing coverts 

 buffy. 



The Swainson's Thrush is the commonest of the North American 

 thrushes that migrate through or winter in Panama. It breeds across 

 much of northern North America and winters from the southern 

 United States to Brazil and Argentina. In extensive netting opera- 

 tions at Almirante, Bocas del Toro, Galindo and Mendez (Bird-Band- 

 ing, 1965, p. 234) found during the fall of 1963 that this species formed 

 76 percent of all migrant thrushes netted. They captured 3120 Swain- 

 son's, compared with 743 Gray-cheeked Thrushes, 145 Veeries, and 95 

 Wood Thrushes. Galindo and Mendez, and Willis (Living Bird, 1966, 

 p. 201), who spent the fall of 1960 on Barro Colorado Island, found 

 Swainson's Thrushes commonest in October, "scattered" or "rare" in 

 winter, and uncommon in spring. Griscom (Bull. Mus. Comp. Zool., 

 vol. 78, 1935, p. 361) calls it "casual" in summer, based on a specimen 

 taken on July 4 at Perme, San Bias. The earliest fall specimen in the 

 Smithsonian collection is from October 10, 1960, taken at Almirante, 

 Bocas del Toro, and the latest spring specimen was collected on the Rio 

 Jaque, Darien on April 11, 1947. 



Ripley (Checklist Birds World, vol. 10, 1964, pp. 171-173) lists 4 

 races of the Swainson's Thrush. They are analyzed in detail by Bond 

 (Proc. U. S. N. M, vol. 114, 1963, pp. 373-387). Specimens of all 4 

 have been collected in Panama. C. u. swainsoni is the form that regu- 

 larly occurs here; it may be found in wooded and shrubby areas 

 throughout the Republic from lowlands and foothills, up to at least 

 1800 m in the Chiriqui highlands, and on the Pearl Islands. 



CATHARUS USTULATUS ALMAE (Oberholser) 



Hylocichla ustulata almae Oberholser, 1898, Auk, 15, p. 304 (East Humboldt Mts., 

 opposite Franklin Lake, Nevada.) 



Characters. — Upper surface distinctly grayer than in other forms. 



Measurements. — Males (10 from Alaska, Mackenzie, and Alberta), 

 wing 96.1-102.1 (99.8), tail 66.1-70.6 (68.8), oilmen from base 14.2- 

 17.7 (16.4), tarsus 27.0-28.7 (27.9) mm. 



