Ardea
Official journal of the Netherlands Ornithologists' Union

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Feekes F. (1981) Biology and colonial organization of two sympatric caciques, Cacicis c. cela and Cacicus h. haemorrhous (Icteridae, Aves) in Suriname. ARDEA 69 (1): 83-107
Two sympatric colonial caciques, Cacicus c. cela and Cacicus h. haemorrhous were studied in Suriname (South America). Pure and mixed colonies are common, but C. haemorrhous prefers unbroken high forests and C. cela breeds in more open country. C. haemorrhous associates with C. cela. and other related species in less preferred, open and wet habitats. Distribution in South America also indicates that C. haemorrhous avoids large open spaces and wet forests. An attempt was made to evaluate the roles of nest-site selection, foraging strategies and anti-predator behaviour in the colonial organization of the two species. Both species are not selective for nest trees, but require a wide view. In Suriname such trees are abundant. The diet of adults and nestlings consists of fruits and insects. There are no indications of a temporary concentration on particular fruiting trees, since 1) a great variety of fruits is fed to nestlings within short periods, 2) flight directions from the nest tree are stable throughout the breeding cycle and depend on features in the landscape. Anti-predator strategies are highly developed: penduline nests are built at terminal twigs, males act as sentries, alarm calls and fleeing at the approach of predators, joint attack of intruders of the nest tree. It is argued that superfluence of food (since birds exploit numerous food resources) and strong predation pressure are the most important determinants of their social organization. Abundance of food permits gregariousness and absence of pair-formation. Males do not participate in parental care and there are more females than males in and around the nest tree. In groups detection and attack of predators is facilitated, but groups also attract more predators. In these two species males. remain largely hidden in and near the nest tree and come out to attack intruders. It is argued that C. cela is better adapted to presumably more vulnerable life in open country, than C. haemorrhous. Its nests are more densely clustered; fewer males display in few preferred areas, while in C. haemorrhous males do not display in preferred areas. C. cela males have very conspicuous prolonged display with complex song and use a special long-distance song, which is colony-specific. Display of C. haemorrhous is brief and Jess conspicuous and songs are short, simple and not colony-specific. In mixed colonies C. haemorrhous is more shy and it is argued that it seeks protection of the other species.


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