Parental attendance of Chestnut Thrush reduces nest predation during the incubation period: compensation for low nest concealment?

Abstract

A well-concealed nest site is supposed to reduce nest predation risk; however, the expected positive relationship between nest concealment and nest survival does not exist in some passerine species, especially in thrushes. Previous studies have suggested thrushes might be capable of defending their nest against predators and do provide compensation for their low nest concealment, but this mechanism is controversial. We conducted a field experiment on the Chestnut Thrush (Turdus rubrocanus) to test whether parental attendance reduced nest predation risk, and to explore the possible mechanism behind this. In this study, we found that natural nests (with parental attendance) suffered lower nest predation rate than paired re-used nests (without parental attendance). With infrared-triggered cameras, we observed that Chestnut Thrush successfully defended their nests against mice. We identified mice as the main predator in re-used nests, while nest concealment had no significant impact on mice predation. Overall, parental attendance of the Chestnut Thrushes reduced the nest predation risk by deterring opportunistic predators, but not enough to offset the low nest concealment.