352 BIRDS OF THE REPUBLIC OF PANAMA PART 4 



del Toro, on the Rio Ciri Grande, Province of Panama, and apparently 

 in western Panama east to the western part of the Canal Zone all nest 

 solitarily, while in the eastern part of the Canal Zone (Madden Forest 

 Preserve) eastward, colonial nesting apparently prevailed, although 

 some solitary nesting occurred. 



The nest is a long pouch — one measured 64 cm in length — placed in 

 a tree from 4 to 33 m from the ground; often a tree containing a wasp 

 colony is selected. Skutch found birds building nests in late April and 

 early May. One nest contained two eggs on April 24; they were "white 

 marked with a few light brown and blackish spots and some short 

 scrawls on the thicker end, still fewer elsewhere." Incubation is per- 

 formed exclusively by the female. At one nest two eggs hatched by May 

 1; the young had pink skin, no down, and mouth interiors of pale pink. 

 At 3 or 4 days their pinfeathers were sprouting and their eyes were 

 partly open. The young were fed insects;- unfortunately this nest was 

 destroyed, so that Skutch could not observe their growth. Young, well- 

 grown birds still accompany their parents and are fed by both of them; 

 Skutch found one such family in mid-March, when a juvenile was be- 

 ing fed by both parents and had little success finding food on its own. 



After breeding, these solitary nesters often gather in bands. 



The voice of C. u. microrhynchus is far more musical than that of 

 the Yellow-rumped Cacique, C. cela; it consists chiefly of loud, clear 

 whistles. On June 23, 1952, Eisenmann noted a vocalization as a rather 

 human-sounding whistle wheew-whee-whee-whee-wheet, sometimes ab- 

 breviated to wheew-whee-wheet. Characteristic also was a rather sweet, 

 tremulous, though burry, or throaty, whistle, ree-oo, ree-oo varied to 

 kreeoo or shreew-shreew. 



An occasional adult male of this race shows a faint swelling on the 

 outer face of the base of the mandibular rami, an indication of approach 

 to the condition found in C. u. pacificus, but this is not usual. The 2 

 races are similar in size. 



CACICUS UROPYGIALIS PACIFICUS Chapman 



Cacicus uropygialis pacificus Chapman, Bull. Amer. Mus. Nat. Hist., vol. 34, Dec. 

 30, 1915, p. 657. (Alto Bonito, Rio Sucio, Antioquia, Colombia.) 



Characters. — Bill larger, with the bases of the mandibular rami dis- 

 tinctly swollen; concealed white on bases of the feathers of the dorsal 

 area much more extensive, both in distribution and on the individual 

 feathers. 



Measurements. — Males (10 from Darien and Colombia), wing 



