Vertical stratification of birds in different vegetation types along an elevation gradient in the Eastern Himalaya, India

Abstract

Abstract We examined the vertical stratification of birds in relation to foliage in different vegetation types along an elevation gradient in Sikkim, Eastern Himalaya, India. We used variable-width point count methods for sampling birds spread across 20 transects along an elevation gradient from 300 m to 3,800 m above mean sea level. We estimated species richness, abundance and Shannon-Weiner diversity (H′) of birds in seven height categories (0 m, 0–5 m, 5–10 m, 10–15 m, 15–20 m, 20–25 m and >25 m). Foliage structure and complexity of vegetation was assessed along all transects following Erdelen (1984) and Jayson and Mathew (2003). Birds displayed distinct vertical stratification in terms of species richness, abundance and diversity in Sikkim. Overall, maximum species richness (231) was observed at 0–5 m height followed by 5–10 m, 10–15 m and the ground layer (0 m). There was no significant difference in stratification pattern among elevation zones. Each height class harboured distinct species compositio...