Observations of Brown-Throated Martin Riparia paludicola Nesting and Roosting in Burrows of European Bee-Eaters Merops apiaster

We present cases of Brown-throated Martin Riparia paludicola roosting and nesting in disused burrows of European Bee-eaters Merops apiaster, and participating in the latter's nest defense. In one case, Brown-throated Martin nested in the same burrow between two successive nesting episodes of European Bee-eater. Brown-throated Martin collectively mobbed a snake that was predating the European Bee-eater's chicks inside the “shared” burrow, suggesting possible benefits for bee-eaters whose burrows are also used by Brown-throated Martin. The martins benefit by gaining nesting and sheltering sites in winter. However, negative implications of this mutualistic relationship, such as competition and parasite transmission, are still to be investigated.