On the types of resistence to predation in birds'nests of a delimited area of tropical rainforest in Peru

The study area of 2 km2 is situated at Río Llullapichis, an affluent of Río Pachitea (central eastern Peru) at about 300 m above sealevel. It comprises mostly of primary rainforest, and there is some secondary growth, a very small garden area, and the river, some 40 m wide, with its natural riverside plant comunities. The study area is surrounded by large areas of primary rainforest. A list of predators is presented. Among them monkeys and toukans are of major importance. As predation of nestlings and eggs is very high a strong selection pressure acts continuously on the birds. To breed successful they have to build their nests in special places or defend them in another way. A synopsis of the types of resistence to predation in the birds'nests is given, distinguishing the following categories: nesting on places difficult to reach, nesting in holes (in trees, in the ground), armourment of the nest (breeding in hard constructions made either by the bird itself or by other animals), camouflage, social nesting and defence, defence by the parents, defence by other animals, desception of the predator, and reduction of the nest. Special attention is given to camouflage and types of sociability. Some adaptations of ground breeders are presented. To show examples of convergence, two types of nests (simple open nests consisting mainly of twigs, and closed domed nests) are treated shortly. Finally the effects of the types of resistence to predation are discussed. Mostly more than one of the above mentioned methods of resistence can be found in one nest. We see that the success is of relative value only, but, of course, it is effective enough to maintain the natural density of population which is low in most of the species of birds in the study area.