372 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 30 



They can doubtless be reached by tree snakes, though I have no 

 evidence of their being preyed on by these, or by other reptiles. 

 Possibly marmosets may be able to approach them, but we have 

 never known them to do so. Furthermore, any diurnal enemy 

 would doubtless be subjected to attack from the sharp, strong bill 

 of the female, and perhaps also of the male Zarhynchus. It is, 

 however, a nocturnal winged foe that proves to be one of the most 

 serious enemies of the oropendola. This statement is based on 

 observations made on group 1, 1928, and recorded in my journal for 

 January 25, as follows : 



Seven-thirty a. m. Some mishap has befallen group 1 (containing 8 nests) 

 during the night. Nest No. 3 is hanging upwind across the lower part of 

 No. 4, and has a large, round hole in its bottom, evidently made from without. 

 No. 5 has a similar opening. Nos. 2 and 4 each have a small round hole in 

 the side near the bottom. I showed these nests to Donate, who at once said : 

 "El buho " (local name for Pulsatrix prrspicillata) and added that early one 

 morning in the preceding year he had seen an owl fly from its perch in the 

 dead tree adjoining the sand box tree and pick at the oropendola nests. Cer- 

 tainly whatever did this work had wings. 



The owl named is seen or heard about the clearing nightly. 

 Donato, our resident factotum, is a careful observer, and it is prob- 

 able that his identification of the marauder is correct. All the nests 

 mentioned were begun on January 2 and it is possible may have 

 contained eggs though I had no record of the birds' sleeping in their 

 homes. The owners of Nos. 2 and 5 returned to their homes and 

 were evidently incubating as late as February 3. 



Apparently the attack of the owl or owls created a condition 

 which made the remaining birds in the group more susceptible to 

 persecution by Legatus and eventually the whole group site was 

 abandoned. On former occasions I had seen holes an inch and a 

 half in diameter at the side of the nest bag about on a level with the 

 nest and supposed that they were made by the owner; but if they 

 are made by the foot of an owl reaching in while clinging to the 

 nest, it is evident that the home of Zarhynchus is far from 

 impregnable. 



PARASITIC BIRDS 



Zarhynchus^ while nesting, is parasitized by two other birds, one 

 of which, in effect a large cowbird {Cassidix), visits the colony from 

 time to time to deposit its eggs, while the other, a flycatcher 

 (Legatus), is a permanent resident who in seeking to gain possession 

 of an oropendola nest for its own uses becomes a community aflSiiction 

 of the first magnitude. 



Cassidix oryzivora. — It has long been Iniown that Cassidix 

 oryzivora is parasitic on certain members of the oropendola-cacique 



