Bird Predation on Concealed Insects in a Reed-dominated Estuarine Tidal Marsh

Insectivorous birds can provide important ecosystem services, including regulating insect populations. The function of insectivorous birds in wetland ecosystems, such as tidal marshes, however, remains largely unexplored. Most studies of top-down interactions between insectivorous birds and herbivorous insects focus on insects in exposed-feeding guilds, but rarely on those in concealed-feeding guilds. In a reed-dominated estuarine tidal marsh, we examined the impacts of insectivorous birds on three groups of insect herbivores with concealed-feeding habits, including scale insects, gall-forming fly larvae, and stem-boring caterpillars. Insectivorous birds attacked 14.0-75.8% of reed shoots infested with scale insects, 13.3-20.7% with gall-forming fly larvae, and 8.0-100.0% with stem-boring caterpillars. Bird predation also significantly changed the abundance of herbivores, reducing scale insects by 36.7-85.9%, gall-forming fly larvae by 33.3-46.0%, and stem-boring caterpillars by 77.0-100.0%. Scale insects and stem-boring caterpillars suffered bird predation during different periods of the growing season. Our study demonstrated significant impacts of bird predation on concealed-feeding insects in a reed-dominant tidal marsh, highlighting the role of insectivorous birds in vegetated wetland ecosystems.