On nest-site copying, owner aggression, and mimicry: the adaptive significance of interspecific information use in a landscape of fear

Abstract

There is increasing evidence for species using information from heterospecifics to assess predation risk or habitat quality. Notably, a series of influential studies, using geometric symbols added to nest boxes, has shown that migratory flycatchers copy tits’ apparent nest-site preferences and settle in nest boxes bearing the same symbol as tits’ nest boxes. This “Selective Interspecific Information Use” hypothesis was recently challenged by the “Owner Aggression” hypothesis, stating that nest occupancy patterns are instead driven by tits aggressively excluding flycatchers from particular empty boxes to use as potential re-nesting sites after nest predation. Here, I propose the “Adaptive Interspecific Information Use” hypothesis, which outlines the predicted fitness benefits of nest-site copying or rejecting, and, importantly, provides an explanation for inconsistent experimental results to date. Indeed, neither previous hypotheses satisfactorily explains why flycatchers switch from copying to avoiding tits’ preferences, when tits’ clutch sizes are small or tits are at the laying stage. Adding to the recent debate, I show how predictable changes in nest predators’ search image and tits’ anti-predator behaviour may explain this variation. Indeed, incubating tit species aggressively defend their nest against nest predators, including by emitting snake-like vocalisations, which may generally deter predators from boxes bearing a tit nest symbol. By contrast, the undefended tit nests—which occur during laying before incubation starts, or potentially in individuals with small clutches—are easy prey that predators may specifically target. If predators cue on tit nests’ symbol, I therefore predict that, to reduce predation risk throughout the season, flycatchers may switch from avoiding the symbol of undefended tit nests to preferring the symbol of tits incubating large clutches. I propose experiments to test these predictions. Overall, considering nest-site copying in the landscape of fear framework, rather than invalidating the Selective Interspecific Information Use hypothesis, may be key to understand its evolution.