SHORT COMMUNICATION Who bullies whom at a garden feeder? Interspecific agonistic interactions of small passerines during a cold winter

Abstract Interspecific agonistic interactions are impor-tant selective factors for maintaining ecological niches of different species, but their outcome is difficult to predict a priori. Here, we examined the direction and intensity of interspecific interactions in an assemblage of small pas-serines at a garden feeder, focussing on three finch species of various body sizes. We found that large and medium-sized birds usually initiated and won agonistic interactions with smaller species. Also, the frequency of fights in-creased with decreasing differences in body size between the participants. Finally, the probability of engaging in a fight increased with the number of birds at the feeder