Observing Nocturnal Birds Using Localization Techniques

Although nocturnal birds in Japan are rare, they often play critical roles in the ecosystem. Because they are elusive, however, the accurate and efficient monitoring of such birds, has been a challenge for field researchers. Furthermore, difficulties multiply when the population size of the target species is decreasing. This paper introduces recording examples conducted in the field to secretively monitor nocturnal birds in different environments, using localization techniques. We observed two different species, the ruddy-breasted crake (Porzana Fusca) in wetland and the Ural owls (Strix uralensis) in a forest, both of which are rare and their conservation is of environmental concern. We localized the territorial calls of crakes, and the feeding and fledgling scenes of owls, derived from one or multiple microphone arrays. The localized sounds successfully captured the fine-scale movements of these species in space and time, which cannot be easily obtained from any other monitoring method. Our results provide the first cases of monitoring such rare species using microphone arrays in the field.