The breeding grounds of a number of native bird species, including skylarks and shrikes, have sharply decreased over the past two decades, but several species imported originally as pets are becoming established in the wild, according to an interim report on bird habitats released Tuesday.
Some 1,700 members of the Wild Bird Society of Japan conducted a nationwide study for the Environment Agency from 1997 to 1998 into the breeding grounds of 600 types of wild birds in Japan, according to the report.
The breeding grounds of seven of them, however, including the once common triller, skylark and thick-billed shrike, have declined markedly since the previous survey in 1978, the report says.