Functions of Snake Sloughs in Bird Nests Vary with Habitats: A Test of the Anti-Predation Hypothesis.

Snake sloughs in bird nests can reduce nest predation and serve as an anti-predator strategy. However, the anti-predator function of snake sloughs in nests has only been tested twice, and it is difficult to speculate around the origin of the differences, which may well include habitat, as predator species and predation risk vary in different habitat types. Habitat would be a good place to speculate as to how differences in habitats could explain differences in responses by nest predators. Thus, we selected three different habitats, namely, the Diaoluoshan National Nature Reserve in Hainan (DLS, tropical forest), the Hainan Normal University campus (HNU, urban area), and Qingchuifeng National Forest Park in Hebei (QCF, suburban area), to verify the anti-predator function of snake sloughs in bird nests. The experimental results showed that snake sloughs in the nests reduced the predation rate of the experimental nests in HNU, whereas no such effect occurred in DLS and QCF. This suggests that the anti-predatory function of snake sloughs may not be the same over some environmental gradients and could be dependent on the species of nest predators and food resources in the habitat, which does not apply to all types of habitats.