336 BIRDS OF THE REPUBLIC OF PANAMA PART 3 



pure white, and the rest of the under surface and rump gray. The 

 subspecies Manacus manacus abditivus meets and to some degree 

 overlaps the range of Manacus vitellinus milleri along the lower and 

 middle Cauca \^alley. 



On the Caribbean slope in Costa Rica beyond Bocas del Toro there 

 is a third bird of this group, Manacus candei, in which the male, ex- 

 cept for the black crown, has the entire anterior half of the body, in- 

 cluding most of the upper and lower wing coverts and the axillars, 

 pure white, and the remainder of the lower surface bright yellow. 

 This ranges north without appreciable variation to southeastern 

 Mexico. It is recorded as common in the northern part of Caribbean 

 Costa Rica but uncommon in the south toward Panama. Slud (Bull. 

 Amer. Mus. Nat. Hist., vol. 128, 1964. pp. 238-239) in outlining the 

 Costa Rican distribution, adds parenthetically "and almost certainly 

 adjacent Panama." But of its occurrence on the Panamanian side 

 of the boundary at the Rio Sixaola as yet there has been no record. 



The relationship of these three entities is a matter of interest. 

 It may be postulated that the original stock was of South American 

 origin that has spread north through the Isthmus of Panama, perhaps 

 since the close of Pleistocene time. That the three as they are now 

 present are allied is evident, but opinion as to the type of this rela- 

 tionship may vary. Males of all three reproduce through a method 

 in which from one to several are resident in a limited area where 

 each has a small bare territory cleared on the ground. To this they 

 attract females through active displays, accompanied by peculiar 

 calls and mechanical sounds. After mating and fertilization, the labor 

 of nest construction, incubation, and rearing of young is the function 

 of the female alone. Recently. Dr. Haffer. familiar in the field with 

 those of Colombia, (Amer. Mus. Nov., no. 2294, 1967, pp. 12-17) 

 suggests that the three "have not reached full species status, still 

 replacing each other geographically and hybridizing along narrow 

 zones of secondary contact," so that they are to be treated as a group 

 or "semi-species within the species unit Manacus manacus (Lin- 

 naeus)." As argument, he cites highly interesting observations by 

 E. O. Willis in the middle Cauca Valley near Caucasia, Antioquia, 

 where males of M. m. abditivus and M. v. milleri both were displaying 

 in "an isolated woodlot ... no more than ten meters apart. . . . 

 Out of some ten males displaying in this small dancing ground, two 

 at the north end were white [abditivus], one or two at the south end 

 were yellow [tnilleri] and six or so in between were pale yellow 

 hybrid [abditivus X milleri]." He collected one pale yellow and 

 one white bird as specimens. 



