they seem to prefer warm, comfortabli comfortable ease knewma. the birds had lost their natural sense to migrate and didn't bother to fly. >> translator: we wanted to revive the annual migration of the geese. they shouldn't stay in japan all yearlong. we decided to capture themm and brought them back to the zoo. >> reporter: he realized that getting t the birds to migrate meant releasing them in their traditional breeding grounds in russia. the coral islands were once japanese territory but russia took them over in 1945. it was basically impossible for japanese scitizens to conduct research on the islands. bubut everythgg changeded with collapse of the soviet unionn i 1991. thee cold war was over. this opened the door to further collaboration between japanese and russian researchers. it also meant that releasing cackling geese w was now pososs. >>>> translator: we f found one suitabable island without foxox. the geese are very small and foxes are really d dangerous prededators. >> repororter: dozens of geese bred in captivity in j and russia were