Intra- and interspecific social information use in nest site selection of a cavity-nesting bird community

Animals need information about local conditions to make optimal fitness-enhancing decisions such as where to breed. Information can be acquired by personal sampling of the environment, but it can also be acquired from other individuals. The latter is termed social information use. Social information use has gained a lot of attention in modern ecology because it affects principal ecological phenomena such as animal distribution and resource use. Social information use is not restricted to obviously cognitive mammals and birds but is also found in e.g. reptiles, fish and insects. Social information use studies have thus far been concentrated on situations with one social information user and one (often the same) source species. The community-wide consequences of social information use have almost exclusively been considered in theoretical studies. In this thesis, I studied empirically social information use in the nest site selection within and between species in a cavity-nesting bird community consisting of the collared flycatcher (Ficedula albicollis), the great tit (Parus major) and the blue tit (P. caeruleus). I studied social information use on two time scales: social information gathered just before a breeding attempt, and social information gathered already during the previous breeding season for the following year’s breeding attempt. I used experiments in which different white geometric symbols represented nest site choices of earlier settled tutors and empty nest boxes, and I observed the symbol choices of later-breeding individuals. The symbol approach eradicates bias from innate and learned preferences enabling strong inference. My results demonstrate that collared flycatchers use social information from both conand heterospecific tutors in different situations in a flexible manner. Hence, social information use seems to be context-dependent. Furthermore, I show that great tits avoid choosing nest site characteristics which were associated with either conor heterospecifics nests the previous year and prefer symbols which depicted an empty nest box the previous year, probably to avoid nest ectoparasites. I also show that in great tits the male has greater influence on nest site selection than previously assumed even though the female builds the nest. My thesis deepens our understanding about the complexity of social information use and highlights its significance in future ecological research.