The positive relationship between species abundance and range size is considered to be general. However, many studies focusing on tropical mountains and islands have found an irrelevant or negative abundance-range size relationship, probably caused by the high proportion of endemic species with high abundance and large range size. The aim of this study was to 1) explore the bird elevational abundance pattern; 2) test the abundance-range size relationship of overall breeding birds, endemic species, non-endemic species, and the difference between mean abundance and elevational range center of endemic species and non-endemic species along the elevation gradient (2350-4950 m) in Lebu Valley, eastern Himalayas. Our results showed that the bird elevational abundance pattern was a hump-shaped pattern. The abundance-range size relationship of breeding birds and non-endemic species was both positive. But the abundance-range size relationship of endemic species was not correlated. Besides, the abundance and elevational range center of endemic species were higher than those of non-endemic species. The result demonstrated that the endemism of regional birds influenced the abundance-range size relationship, and the differences of regional species composition caused by geographic isolation were one of the important reasons for the variations of pattern of the abundance-range size relationship.