CLIMBING BY BLACK RAT SNAKES ON CAVITY TREES OF RED-COCKADED WOODPECKERS

Black rat snakes (Elaphe obsoleta obsoleta) are predators of nesting birds (Fitch 1963, Ernst and Barbour 1989:82), including red-cockaded woodpeckers (Picoides borealis) (Jackson 1978). These woodpeckers excavate resin wells that cause the tree to exude resin around the cavity entrances of roost and nest trees, and resin impedes climbing by rat snakes (Jackson 1974, Rudolph et al. 1990). In North Carolina, predation was not a critical source of mortality in a relatively large population of red-cockaded woodpeckers (Walters 1990), especially when compared to widespread habitat loss (Ligon et al. 1986). However, all sources of mortality are of concern in small and isolated populations because of vulnerability to extirpation (Lennartz and Stangel 1989). In this study we examined (1) frequency of climbing by black rat snakes on cavity trees of red-cockaded woodpeckers, (2) potential predation by black rat snakes on the woodpeckers, and (3) effectiveness of net snake traps and an excluder device (or snake guard) in preventing snake climbing on trees containing woodpecker nests or roosts. Reducing losses of eggs, nestlings, and adult woodpeckers could help stabilize small populations of red-cockaded woodpeckers while habitat quality improves.