Habitat and Its Spatial Structure of the Blue Rock Thrush—Invasion into Inland Cities—

Abstract

Although the original breeding habitat of the Blue Rock Thrush Monticola solitarius is the seacoast, it has started breeding within inland cities of Japan in recent years. We studied its ecology and behavior from 2011 to 2012 in Hyogo Prefecture, in a town situated 20 km from the seacoast that was newly developed 30 years ago. The thrush was present throughout the year round within the town, and its distribution was concentrated in the area of tall buildings where males established breeding territories. Territorial males sang more frequently at higher places than at lower places, and each tried to take a position higher than his neighbors in territorial disputes, which suggests that the thrush defended its territory by singing on tall buildings. In contrast, the thrush foraged among grassland and hunted small animals living on the ground surface. It is suggested that the set of the tall building and the grassland on the ground, which resembles the set of the cliff and the open ground on the seacoast in spatial structure, form a preferable habitat to this species. The Blue Rock Thrush is considered to have invaded into the urban area by adapting themselves to the newly-born environment created by humans.