112 BIRDS OF THE REPUBLIC OF PANAMA — PART 2 



has been an average difference in size, the western form being slightly 

 larger. The overlap between the two, however, is so great that this 

 does not suffice to identify many individuals during migration. The 

 western subspecies is faintly grayer above, the eastern one browner, 

 a distinction that holds in our considerable series. Females average 

 slightly larger than males in both forms. 



There are no records of the yellow-billed cuckoo on the Pacific 

 side west of the Canal Zone. East of that area the lines of flight 

 include both slopes to and from South America. 



COCCYZUS AMERICANUS AMERICANUS (Linnaeus) 



Cuculus americanus Linnaeus, Syst. Nat., ed. 10, vol. 1, 1758, p. 111. (South 

 Carolina.) 



Characters. — Slightly deeper brown on the entire dorsal surface, 

 including the tail; average size slightly smaller, but much overlap 

 with the western race. 



Measurements. — Males (10 from eastern United States), wing 

 138.5-145.1 (141.5), tail 135.1-148.0 (138.2), culmen from base 25.5- 

 29.0 (27.0), tarsus 23.3-27.2 (25.0) mm. 



Females (10 from eastern United States), wing 143.6-149.3 

 (146.0), tail 135.7-148.6 (141.4), culmen from base 25.3-28.8 (27.6), 

 tarsus 24.0-28.0 (25.8) mm. 



Migrant from the north. Tolerably common; recorded in fall 

 migration September 1 to November 24, but mainly during October ; 

 found more rarely in spring, in April. 



The U.S. National Museum has a male taken near Cocoli, Canal 

 Zone, September 1, 1955, by collectors for the Malaria Control Ser- 

 vice. Major General G. Ralph Meyer, in his notes, recorded another 

 seen at Fort Sherman on the same date in 1940. The only other re- 

 port for this month is of 1 collected at Perme, San Bias, September 30, 

 1929, by H. von Wedel. Most of the specimen records are for the 

 month of October. A few have been found during November, with 

 the latest date 1 captured November 24, 1962, near Corozal, Canal 

 Zone, by Dr. Nathan Gale. 



In northward passage I recorded 1 in 1949 near Chepo, April 17, 

 and on April 20 encountered a small flight. Another report is of 1 

 seen April 30, 1951, on Barro Colorado Island by Nicholas Collias. 

 A specimen in the collection of the Gorgas Memorial Laboratory was 

 taken at Almirante, April 19, 1963. 



