THE NESTING HABITS OF WAGLER'S OROPENDOLA ON 

 BARRO COLORADO ISLAND ^ 



By Frank M. Chapman 



[With 8 Plates] 

 INTRODUCTION 



The field studies on which this paper is based were made at the 

 station of the Institute for Research in Tropical America, on Barro 

 Colorado Island. Canal Zone, Panama. They cover the grreator part 

 of three nesting seasons, and the period immediately preceding them, 

 as follows: (1) December 27, 1925, to February 20, 1926; (2) De- 

 cember 22, 192G. to April 2, 1927; (3) December 22, 1927, to April 1, 

 1928. During tlie first season, only part of my time was given to 

 this work; the second and third seasons it was my chief occupation. 



The colony of birds under investigation nested in a sand-box tree 

 {Ilura crepitans) growing about 100 feet from the northerly corner 

 of the institute's main building; a situation favorable for continuous 

 observation of the birds from the time of their first appearance in 

 the morning until they retired in the evening. On the other hand, 

 the nature of the nesting sites prohibited examination of the contents 

 of the nests in situ and the only specimens of nests, eggs, or young 

 obtained were the few that fell through the accidental breaking of 

 the limbs to which the nests were attached. These gave a limited 

 amount of data with wliicli to check conclusions based on observations 

 made from a distance. 



In 1924, when the institute's station was established on Barro Colo- 

 radf), a colony of oropendolas occupied a tree about 100 feet from tho 

 one now used. On June 2G, 1925, possibly because it was deprived of 

 the protection of the trees that had grown near it, this tree fell before 

 the wind. It contained 57 nests. The following nesting season the 

 I)irds selected the tree now used. The present tree, therefore, was 

 apparently chosen because of its proximity to the one which fell, 

 rather than for its special fitness in affording suitable nesting sites. 

 It is a sand-box tree 132 feet in height, growing from near the bottom 

 of a steep slope about 30 feet below the level on which the laboratory 



> Reprinted by permission from the Bulletin of the American Museum of Natural 

 History. Vol. LVIII. 



347 



