354 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 30 



breed after the rains begin, though whether their activities repre- 

 sent an actual second breeding season or are individual I am unable 

 to say. I, myself, have not been on Barro Colorado between April 2 

 and December 22 and for the following observations, made during 

 this period, I am indebted chiefly to Dr. J. Van Tyne of the 

 University of Michigan. 



Dr. Van Tyne writes that only one of the 57 nests in the tree 

 that fell on June 26, 1925, contained anything. This nest held 

 two nestlings nearly ready to fly. A male collected on this date 

 had testes measuring 17 millimeters in length. 



On July 8, 1925, 43 nests were counted in the oropendola colony 

 situated about 400 yards from the laboratory; 8 or 10 birds were 

 present and at least 3 or 4 nests were in use. A male collected at 

 this colony on July 9 had testes measuring 19 millimeters in length. 



In 1927, after my departure on April 2, Dr. Van Tyne reports 

 that on April 5 he saw young fed for the last time in nests that 

 had been begun on January 8 and adds the following observations : 



April 5. Noticed two females fighting over what seems to be a prospective 

 nest site somewhat to the right of any of the present nests. 



April 9. Returning this afternoon from Panama City (Pearl Island trip) 

 I find a whole group (I count a dozen) of new nests being started. The 

 group is situated immediately to the right of and somewhat lower than the 

 old right-hand group of nests. One nest is well along (one-third length) and 

 the rest merely started. I have seen no bird yet using any of the five marked 

 (old) nests. I suppose they are empty by now. Are not the new nests being 

 built for second broods? 



April 11. The nest building is progressing rapidly. There are now 19 nests 

 under construction and more apparently being started. The males have been 

 much more noisy since this new nest building began. Also the false-alarm 

 business (i.e., cackle and dive for safety) has been much more frequent. 

 Leffotiis and Cacicus are much in evidence. Legatus looks into some of the 

 old nests but does not enter. Cacicus merely sits around and sings. 



April 12. I can now count 22 new nests. Only about four of the old nests 

 seem to be still occupied. The females that are building are continually 

 stealing nesting material from each other and from old nests. 



April 14. There are 10 of the nests which are now completed as far as 

 the outside is concerned — they continue to work inside. All of these nests 

 are strikingly shorter than the first brood nest. Most of them are barely a 

 foot long. 



April 19. At 6 a. m. (8 minutes before sunrise) the oropendolas were nearly 

 all at their nests about to begin work. 6.30 p. m. none of the females are roost- 

 ing in the nests yet. But there are several of the old nests still in use. 



April 21. Only 18 of the new group of nests appear to be under active con- 

 struction. Others seem to have stopped entirely and are probably discarded. 

 To-day 6 new nests were started in a separate group about half-way between the 

 two old groups of nests and some 10 feet lower. All are close together on the 

 same branch. Why do they do things by groups like this? What is this 

 smaller group within a nesting colony? 



On April 26 the wet season began — 3.78 inches rain. Rain continued — averag- 

 ing nearly an inch a day. This seems to have stopped the oropendolas. They 



