Effects of local nest predation risk on nest defence behaviour of Japanese tits

Abstract

The behavioural response of individuals to a predator should be related to their long-term predation risk. However, few studies have tested whether and how parents adjust nest defence intensity according to regional nest predation pressure. By monitoring Japanese tits, Parus minor, breeding in artificial nestboxes, we investigated nest predation pressure across China in Jilin (44°N), Liaoning (39°N), Henan (31°N) and Hainan (18°N), and compared nest defence behaviours of parent tits to nest predators among the four populations by conducting dummy experiments. We found that nest predation pressure faced by tits varied geographically. Liaoning tits performed weaker, and Henan tits stronger, defence behaviour against snakes (local high predation risk) than against chipmunks, Tamias sibiricus (local medium/low predation risk). Among populations, Liaoning tits performed the weakest defence behaviour against snakes (regional high predation risk) and Henan tits performed the weakest defence behaviour against chipmunks (regional low predation risk). In addition, hissing behaviour was mainly used to defend against chipmunks, and was rarely shown in Henan where rodent predation risk was low. We conclude that tits adjusted and most likely reduced their defence effort when local nest predation risk was extremely high or low, and reduced the costly hissing behaviour when predation pressure was relaxed from rodents.