環境

Covering wide areas for birds that call during nighttime has been difficult using conventional techniques. This study used 25 timer-enabled voice recorders to survey the nighttime habitat of rare and endangered avian species. Approximately 15,400 hours of audio were collected using this method and was subjected to data analysis including species identification.

The main target species were　Collared Scops-Owl (Otus lempiji), Oriental Scops-Owl (Otus sunia), Ural owl (Strix uralensis), Brown hawk-owl (Ninox scutulata), Japanese night heron (Gorsachius goisagi), and Jungle Nightjar (Caprimulgus indicus). A total of 98 locations within the Tama river upstream region and mountainious regions in Tokyo were selected for survey.

Of the 98 locations surveyed, Ural owls were recorded in 61%, Brown hawk-owls in 33%, Japanese night herons 45%, and Jungle Nightjar 55%.

Collared Scops-Owl vocalization was recorded in 4 locations, 2 of which had confirmed mating behavior. Only 1 location had successful breeding. Oriental Scops-Owl was not recorded in any location.

Here I report the survey results together with discussion on the current situation of these avian species and potential conservation methods.