Previous studies on urban bird diversity have paid attention to green spaces. However, non-green spaces in urban areas may also be important for bird species nesting in artificial structures. We established a study area in Hakodate City, Hokkaido, Japan, and searched for all nests of birds breeding in the area. We found that 15% (N=22) of these nests were built on natural substrates and 85% (N=129) on artificial substrates. Of the 14 species recorded nesting, eight species nested only in natural substrates and four species nested only in artificial substrates.