Bird Community Dynamics i Relation to Water Level Fluctuation in Koshi Tappu Wildlife Reserve

Abstract

Land cover was classified using satellite image in to four classes. Supervised method of classification was used to analyze change in microhabitat. Study area was classified into four groups according to availability of water level, i.e. Land, Shallow water, Wet-Muddy flat, Deep water. Wetland bird community was classified into four groups according to morphological adaptation i.e. Swimmers, Waders, Shorelines and others (which do not fall in above three categories). Wetland bird survey was conducted in four different seasons of 2018/2019. Bird survey was carried with continuous point transect method. A total of 1526 individuals of birds belonging to 53 species 17 families and 10 orders were recorded, among them 15 species of swimmers, 20 species of waders, 9 species of shoreliners and 7 species of others (river birds) were recorded. Pearson correlation test was used to establish the relation between bird community and landscape classes. Highest water level was observed in summer and lowest in autumn. Shannon diversity (H) was maximum of, 2.817 at intermediately disturbed site and lowest at the most disturbed site of, 0.636 both in winter season. Tukey HSD test, showed that bird community assemblage in summer and winter was significantly different. Regression analysis revealed that as water level decreases diversity and abundance of Waders increases. Canonical correlation analysis between bird and microhabitat showed that, Waders prefer open water and Typha spp. Wet-muddy flat habitat was favored by most of the species. Classification of microhabitat with remote sensing in each season showed that landscape composition has changed significantly from summer to winter. Swimmers showed significant positive correlation with Shallow water class (r=0.93). Shorelines also showed significant positive correlation with shallow water class (r=0.94) and slight positive correlation with wet muddy class (r=0.64) and with deep-water class (r=0.644) whereas significant negative correlation(r=-0.93) with land class. Waders showed significant negative correlation (r=-0.72) with deep-water class and shallow water class (r=-0.18) whereas positive correlation with wet-muddy and slight positive correlation(r=0.07), with land waders showed high correlation(r=0.06) with wet-muddy class. The study revealed that bird composition (NMDS F = 3.10; p < 0.0001, Stress value=0.14) was significantly different in four different seasons. This study suggests that water level fluctuations is one of the major factors, which influences the abundance, and composition of Wetland dependent birds.