The nest concealment is often observed in Passeriformes, however, such behavior is unclear in large birds. We evaluated the effect of visibility on nest selection of oriental white stork using GIS.

Eleven nesting points of oriental white stork in Toyooka Basin in 1960's were identified and mapped on GIS. For the reference, evenly spaced points at 100 m interval (N = 13509) were created on GIS within 500 m from the bottom of the basin.

The areas of the paddy field and the open water within short (500 m) and long (2000 m) distances from each nesting point, as well as those from each reference point, were calculated based on land use map. On the other hand, the area of the viewshed in the basin within the same distances from each nesting point, as well as those from each reference point, were calculated using 10 m DEM.

To clarify the preference of nesting site, the results were evaluated using the generalized additive model. It revealed that storks selected moderate viewshed sites, as well as those including larger area of paddy field within the long distance. This means that a stork considers both the accessibility to foraging sites and the defense form the competitor or enemies simultaneously when it chooses a nest site.