A monotonic decline in species richness and diversity with increasing elevation has often been considered as a general pattern, but recent evidence suggests that the dominant pattern is hump-shaped or unimodal with maximum richness occurring at some mid-elevation point. This study was conducted in Kheyrud forest, Mazandaran province. The study area was divided into six elevation levels according to plant communities. Sampling was carried out in mid-spring at 163 random sampling points, which were located with a minimum distance of 250 m apart, as well as a minimum distance of 25 m from the edge of forest. We applied "unlimited radius point count" using "sit and wait" method to count observed and/or heard bird species from dawn until 10:00 am, lasting on average 10 minutes, and avoiding windy and rainy weathers. Our results revealed the existence of significant differences in richness and diversity between elevation classes. Also, we found a hump-shaped pattern of bird species richness and diversity against elevation, reaching the maximum at mid-elevation. These results highlight the importance of forest communities at mid-elevation in North of Alborz Mountain Range and suggest that silvicultural practices should be managed to conserve biodiversity at this elevation zone.