FAMILY PARULIDAE 



249 



The main migration periods are September to mid-October and early 

 February to mid-March; during the spring migration period nearly all 

 the birds I collected were heavy with fat. For the most part, this species 

 leaves Panama relatively early. In areas where they are common in 

 mid-winter, such as Juan Diaz, Province of Panama, they have already 

 decreased markedly by the beginning of March: in 1976 Ridgely found 

 more than 40 there on January 24, but only 2 on March 10. They may 

 remain more numerous later westward; Ridgely found more than 30 in 

 mangroves at Estero Rico, western Chiriqui, on March 6, 1976. 



During migration, Prothonotary Warblers range from mangrove 

 thickets to at least 30 m up in trees in swampy woods. On March 3, 

 1948, I saw dozens feeding in flowering trees at El Rincon, Herrera. 

 They feed commonly in Erythrina trees around Tocumen and else- 

 where in the Canal Zone during January and February; often they are 

 with Tennessee Warblers, orioles, and other species. On February 5, 

 1955, at Isla Taboga, at dusk over 100 descended on a group of trees; 

 they were noisy and easy to approach, but were gone the next morning 

 (F. O. Chapelle in litt. to Eisenmann). The weights of 3 collected by 

 Burton (Bull. Brit. Orn. Club, 1975, p. 85) range from 12.4 to 13.5 g. 



HELMITHEROS VERMIVORUS (Gmelin): Worm-eating Warbler, 

 Reinita Gusanera 



Motacilla vermivora Gmelin, Syst. Nat., vol. 1, pt. 2, 1789, p. 951. (Philadelphia, 

 Pennsylvania.) 



Small; crown striped buff and black; rest of upper surface olive- 

 green; undersurface cream buff. 



Description. — Length 112-131 mm. Adult (sexes alike), crown 

 striped light olive-buff and black; rest of upper surface, tail, and wing 

 coverts olive-green; black line through eye; superciliary pale buff; side 

 of head and upper breast olive-buff; flanks grayish olive; throat and 

 rest of undersurface buffy white; underwing coverts buffy white. 



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

 April), wing 67.0-73.0 (69.6), tail 43.7-55.4 (49.4), culmen from 

 base 13.9-15.6 (15.2), tarsus 17.0-19.3 (18.0) mm. 



Females ( 10 from eastern North America, taken in April and May) , 

 wing 64.1-70.5 (66.9), tail 43.2-53.7 (48.0), culmen from base 13.2- 

 15.8 (14.4), tarsus 16.8-18.6 (17.6) mm. 



Winter visitor from the north. Uncommon but regular in west, rarer 

 eastward; recorded east to the Canal Zone (Barro Colorado Island) 

 and eastern Province of Panama (Puerto San Antonio, on the Rio 

 Bayano), the southern limit of its winter range. Several of the records 



