most other orioles, however, these birds and certain related tropical forms called 

 "caciques" ordinarily nest in compact colonies that may include a hundred or more 

 breeding birds. 



This exhibit is based on field studies made near Escobas, a United Fruit Company 

 plantation in the humid lowlands of eastern Guatemala. It reproduces a small segment 

 of a breeding; colony of Montezuma oropendulas, a common Central .\merican form 

 and one of the largest members of its family. This colony consisted of 138 nests in 

 various stages of completion and use. All of the nests were suspended in a small area at 

 the \ery top of a towering tree that measured almost seven feet in diameter at the base 

 and was well over 100 feet high. Another similar nesting colony may be seen in the 

 right background of the picture. 



These colonies are the scene of great activity during the Ijreeding season. The nests 

 are built by the females, which usually outnumber the males and can be distinguished 

 by their much smaller size. Dr. Frank Chapman's remarks about the nest-building of a 

 related oropendula would serve equally well for the present species. "Building birds 

 often take material from another bird's nest either in their own or an adjoining group. 

 Some birds, indeed, are chronic robbers and steal a large part of their material. 

 Slo\enly builders are more apt to be robbed than those that have no loose tempting 

 ends about their structure. A poor builder is often, therefore, heavily handicapped, for 

 a day's work may be undone in a short time by her thieving neighbors."' 



Besides the filching of building material by their neighbors, nesting oropendulas are 

 constantly harried by other birds. One, a large parasitic grackle, seeks any opportunity 

 to enter an unguarded nest for a moment in order to deposit its eggs among those of the 

 oropendula. Hardly less annoying is the striped flycatcher, which, through sheer per- 

 sistence and aggressiveness, sometimes succeeds in taking over an entire nest for its 

 own use. Certain hawks and owls also prey upon oropendula colonies, but the alert 

 males, w ith little else to do. act as sentinels during the Ijreeding season. 



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