Detecting the nesting suitability of the re-introduced Crested Ibis Nipponia nippon for nature restoration program in Japan

Abstract

The Crested Ibis, became extinct in the wild in Japan in 1981; however, a captive breeding facility was established on Sado Island, Niigata Prefecture in 1999 in the hope of conserving the species. Following successful breeding at the facility, a group of birds was released on Sado Island on 25th September 2008, with further reintroductions in subsequent years. Habitat restoration is also necessary to facilitate the re-introduction program of this endangered species. The aim of this study was to detect suitable nesting areas for the released ibises on Sado Island for subsequent nature restoration. Since little ibis nesting information was available for Sado Island, the nesting model was constructed from nesting information from China, from which results were extrapolated for Sado Island. Land usage was assessed using LANDSAT/ETM+ data for China and SPOT/HRG images for Sado Island. In this study, land-use information was used to define the environmental parameters related to nest site selection of the Crested Ibis. For the nesting model, a generalized linear mixed model, with seven environmental factors, was employed. The multi-spatial scale for Crested Ibis nesting was also analyzed. We took the spatial scale into consideration at intervals of 100m from a buffer size of 100m to 2500m. Because nest site selection was influenced by the results of the previous year, nesting location data in 2005 and 2006 were distinguished and models built accordingly. Several important environmental factors were identified for nest site selection: the ratio of broadleaved deciduous forest to coniferous forest; the shape of the forest edge; and, the distance from rice fields and other wetlands. The model’s accuracy was verified using the Boyce index, and shows the validity of the model’s results. Suitable nesting areas for the Crested Ibis were found mainly on: the Kuninaka plain; the ridgeline between the Kuninaka plain and the Osado or Kosado mountain ranges; the area around Lake Kamo; and, the midwestern area of the Kosado region. Suitable nesting sites for the Crested Ibis were all found to be concentrated in what is known as Yatsuda, a traditional Japanese landscape structure providing a complex mosaic of forest and rice fields with complex ecotones. Eastern Kosado, the region that has been designated by the Ministry of the Environment as the conservation area for the reintroduced birds, was not judged to provide suitable nesting habitat for the Crested Ibis. Unfortunately, no evaluation of habitat suitability was made prior to the release of the first captive-bred Crested Ibis into the wild on Sado Island. Had an evaluation of habitat suitability been performed prior to release, more effective nature restoration could have been planned.