370 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1930 



March 11 (absent March 10). No 5 works casually and ineffectively but at 

 three places, all within a few feet of one another. 



March 12. No. 5 was not seen. 



March 13. No. 5 not seen by me but reported by Mr. W. E. Hastings to have 

 done some work. 



JIarch 14. No. 5 not observed. 



I find no further reference to this bird in my journal until March 

 17 when there is the following entry : " No. 5 works at position No. 3 

 for a few minutes, then disappears. She had made practically no 

 progress since the first day or two." The next and last entry is 

 March 28 when Mr. Hastings reported that a female attended by two 

 males came to the limb on which the new nests had been started and 

 did a few strokes of work. 



If I am correct in identifying the bird that began these nests with 

 the one that had lost her nest 20 feet above the new position, and the 

 record of March 8 seems to justify this belief, it appears that after 

 devoting 36 days to nest building and approximately 12 to incuba- 

 tion she could, after one day's manifestation of interest in the lost 

 nest, return to that part of her annual cycle, which in the normal 

 process of development had been reached when she first began to 

 nest, 58 days prior to her loss. Its promptings, however, were not 

 sufficiently strong and definite to enable her to complete a new nest. 



ENEMIES 



Aside from the parasitic blackbird, Cassidix, and flycatcher, Lega- 

 tus, two other birds were found to attack the oropendola colony on 

 Barro Colorado. Only one of these is diurnal, nevertheless the males 

 are constantly on guard. It is, indeed, their duty to act as watch- 

 men of the colony. While building, the females' attention is of 

 necessity concentrated on their work and until they begin to weave 

 inside the structure they are exposed to attack from birds of prey. 

 The males, however, in spite of their almost constant wooing, are 

 ever on guard and when a hawk is seen they are the first to utter the 

 rapid, cackling alarm note, the females joining them in calling on 

 certain occasions. This is a signal for the whole colony to dive 

 precij^itately into the lower growth of the adjoining forest. 



Turkey buzzards do not, as a rule, evoke this call and generally 

 the white snake-eating hawk {Leucoptemis ghieshr'echti) , a pair of 

 which lived near the laboratory, was permitted to pass unchallenged. 

 But at times even the appearance of these birds, more particularly 

 the latter, was the occasion for an outcry and the accompanying 

 downward rush to cover. Rarely a low-fljdng airplane created 

 alarm. Often the warning cry is given without apparent reason 

 but its cause may have been clear to the birds if unseen by me. 

 Possibly also it may have shades of meaning to which human ears 

 are deaf. 



