Heart rot hotel: fungal communities in red-cockaded woodpecker excavations

Tree-cavity excavators such as woodpeckers are ecosystem engineers that have potentially complex but poorly documented associations with wood decay fungi. Fungi facilitate cavity excavation by preparing and modifying excavation sites for cavity excavators. Associations between fungi and endangered red-cockaded woodpeckers (RCWs) are particularly interesting because these are the only birds that specialize in excavating into the heartwood of living pines, a process that takes years to complete. Using molecular methods, we examined fungal communities in complete and incomplete RCW excavations, and non-cavity control trees. In addition to finding a high diversity of fungi, we found three groupings of fungal communities corresponding to the three groups of trees sampled. We show that trees selected for cavity excavation by RCWs are infected by distinct fungal communities, and propose two hypotheses to explain this outcome: the bird facilitation hypothesis and the tree selection hypothesis.