NESTING HABITS OF OROPENDOLA — CHAPMAN 



351 



Possibly this is one of the reasons, perhaps the chief reason, why birds 

 in the tropics nc^t tliroufrhout the year. The mean temperature for 

 July in Panama is 81.1 ; for February, 80.8°; a difference of only 

 three-tenths of a degree. Comparison of the mean temperatures on 

 Barro Colorado for December and January of the three years covered 

 by my studies of ZarJn/nchus shows a sli«:;ht decrease in the second 

 month the first year, a negligible increase in the remaining two. The 

 data follow : 



Mean Temperature for Deeemhcr and January 1925-1928 



Table of rainfaU, in inehes, on Barro Colorado Island during December and 

 early January, 1925-1928 



DECEMBER 



■ Zarhynchiu began to build nests. 



The end of the wet season, therefore, varied from December 6 in 

 1925 to at least January 12, in 1927. That this variation was not 

 reflected in the dates when the oropendolas began to nest will be se«n 

 from the following data : 



