Information networks among species : adaptations and counter-adaptations in acquiring and hiding information

Social information use is a widespread phenomenon across the animal kingdom and it affects various important aspects of animal behaviour. Animals observe and copy the behaviour of conspecifics and other species on the same trophic level in their own decision-making, e.g., in habitat or mate choice. Copying is adaptive only when it is selective. Thus, it would be important to understand when and which individuals should copy others, and which individuals they choose to copy and what are the consequences of social information use. In this thesis, I experimentally study these questions in wild animals living in natural conditions. By simulating arbitrary preference of great tits (Parus major), I demonstrated that the portrayed fitness does not affect the nest site choices of conspecifics, but the tit pairs with an old male prefer the nest site choices of good and poor conspecifics. Social information use among tits appears to be ageand sex-dependent. Pied flycatchers (Ficedula hypoleuca), however, selectively copy or reject a novel nest site feature preference (symbol attached to the nest box) of great tits experimentally manipulated to exhibit high or low fitness (clutch size), respectively. By offering pied flycatchers choice in nest boxes with alternative contents, I showed that nest take-overs of flycatchers are not a form of social information use, but seem to result from the reduced building effort required. Furthermore, by conducting a decoy and playback experiment, I showed that great tits covered eggs more efficiently in the presence of pied flycatchers. One function of egg covering behaviour seems to be a counter-adaptation to reduce information parasitism by pied flycatchers. My results demonstrate that the social transmission of behaviours across species can be highly selective in response to observed fitness, plausibly making the phenomenon adaptive. In contrast with the current theory of species coexistence, overlap between realized niches of species could dynamically increase or decrease, depending on the observed success of surrounding individuals. The social information revealed by success and behaviour of animals is a resource that can be used or concealed. It is a new kind of evolutionary and ecological factor which may affect the formation of ecosystems and species coevolution.