Abstract: The Mediterranean basin is one the most threatened “hot spots” of biodiversity in theworld due to the important destruction level of its habitats. During the last years, Tlemcen oakforests suffered strong degradations caused by repeated fires and human activity pressure, notablyovergrazing. We analyzed the impact of habitat degradation on the avian biodiversity bycomparing biodiversity measures such as richness, abundance and diversity indices in four oakforest habitats showing increasing degradation levels. In all cases, the habitat degradation levelexplained more than 60% of the variance of these indices. The most degraded habitats sufferedthe strongest biodiversity loss. On the other hand, the functional avian community groups alsoappeared to be affected by habitat degradation: the decreasing number of forest specialist andgeneralist species along the gradient of habitat disturbance benefited to the open field species.These results confirmed that it is necessary to perform urgent conservation actions notably inmature and degraded oak forests.