FAMILY CUCULIDAE 119 



and trisa at Boca de Paya, Darien. Those in Bocas del Toro who 

 spoke English knew it as the old-man-bird, an obvious import from 

 Jamaica where this is the name of another species of cuckoo of 

 similar form. 



The squirrel cuckoos of Central America form an interesting com- 

 plex that, through collections assembled in recent years, now may be 

 understood with greater certainty. Piaya cayana mexicana of the 

 Pacific slope of Mexico, from southern Sonora to Oaxaca, differs 

 from all other subspecies by the cinnamon color of the under surface 

 of the tail (except for the black subterminal bar and the white tip), 

 and much paler coloration. Van Rossem, on the basis of 1 specimen, 

 thought that the birds of southern Sonora carried this lighter color 

 still further, named them extima, but this does not appear valid. 

 This name, therefore, is placed as a synonym of mexicana. Another 

 paler race, P. c. stirtoni van Rossem, found also on the Pacific slope 

 from extreme southwestern Guatemala to northwestern Costa Rica, 

 has the under surface of the tail mainly black ; it is definitely darker 

 than mexicana in addition, and is slightly paler than the following 

 race. 



Piaya c. thermophila Sclater has the darker tail just mentioned, and 

 in addition is darker both above and below. After examination of 

 approximately 100 well-documented skins this name is accepted for 

 the entire population found on the Caribbean slope from Tamaulipas 

 to Oaxaca, Mexico, including the Yucatan Peninsula, and on both 

 slopes from Chiapas through Central America to extreme north- 

 western Colombia, except for the limited area on the Pacific side 

 assigned to stirtoni. Variation is evident in this range, but it is 

 individual except for a minor difference in bill size. In a series of 

 10 of each sex from eastern Mexico the length of the culmen 

 measured from the base is as follows: Males 27.6-31.2 (29.1), 

 females 27.6-31.3 (29.3) mm. In an equal number from Panama this 

 measurement is as follows: Males 30.5-34.1 (32.1), females 30.5-33.5 

 (31.6) mm. Relatively few birds have been examined from Guate- 

 mala, but from Honduras to Costa Rica birds with bill sizes in both 

 ranges are found. The distinction seems too slight and too variable to 

 warrant any separation by name. 



Throughout Panama there is variation in depth of dorsal color. 

 While most of those from the eastern side of the Azuero Peninsula 

 are paler, and those from Bocas del Toro and Darien darker, styles 

 are mixed, as dark birds are found in the Azuero area, and paler 

 examples mixed with the dark series elsewhere. Griscom proposed the 



