344 BIRDS OF THE REPUBLIC OF PANAMA PART 4 



od, during which several may pursue a single female until one has estab- 

 lished his dominance and the other males look elsewhere. At the Barro 

 Colorado colony Chapman studied, females outnumbered males about 

 6 to 1 . Males may accompany particular females as they go off to gather 

 nesting material, but as soon as incubation begins the males loose in- 

 terest. 



The nest itself is a long pouch woven out of lengthy rootlets, tendrils, 

 and fibers that are gathered in the forest or stolen from neighbors. 

 Chapman found nests that measured from 55 to 100 cm in length; the 

 diameter of the pouch was always 19 cm. At the beginning of the sea- 

 son most nests take about 31 days to complete; later, however, they are 

 built more rapidly. The two eggs that form a clutch are "pale blue with 

 numerous irregular shaped brownish-black marks varying in size from 

 a pinpoint to a currant and clustering most thickly about the larger 

 end" (Chapman, op. ext., p. 147). The one egg Chapman was able to 

 measure was 33 by 22 mm. 



The incubation period is 17 days and the young emerge from the nest 

 approximately 33 days after hatching. Incubation and care of the young 

 are performed entirely by the female. The oropendolas have two avian 

 parasites to contend with, the Giant Cowbird (Scaphidura oryzivora) 

 and the Piratic Flycatcher (Legatus leucophaius) . The cowbird is rec- 

 ognized as an enemy from the time the female cowbirds first visit the 

 colony tree, when nests are still under construction; groups of oropen- 

 dolas attempt to drive them away, but inevitably a few cowbird eggs 

 are deposited in oropendola nests. Chapman mentioned no incidents of 

 oropendolas recognizing the strange egg and removing it. The Piratic 

 Flycatcher attempts to harass at least 1 female oropendola to the point 

 where she deserts her nest, which the pair of flycatchers then take over 

 and use as their own. In 1928 a pair of these flycatchers so distracted 

 the birds Chapman was observing that the entire colony deserted its 

 tree. 



This species has often been separated in the genus Zarhynchus. 



PSAROCOLIUS DECUMANUS MELANTERUS (Todd): Crested 

 Oropendola, Charcarero Crestado 



Ostinops decumanus melanterus Todd, 1917, Proc. Biol. Soc. Washington, 30, p. 3. 

 (Las Vegas, Santa Marta, Colombia.) 



Large; a few feathers of central crown elongated, forming a slight 

 crest; all black except for chestnut rump and undertail coverts, and yel- 

 low tail. Bill, extended to form a frontal shield, pale yellowish green 

 or waxy yellow, without dusky tip. 



