Variation in Bird Assemblages Along an Agricultural Intensification Gradient: A Case Study of Olive Orchards in North-Eastern Algeria Bouam, Idriss and Bachir, Abdelkrim Si and Katayama, Naoki, Ornithological Science, 16, 147-157 (2017), DOI:http://dx.doi.org/10.2326/osj.16.147