Normalized difference vegetation index dynamic and spatiotemporal distribution of migratory birds in the Poyang Lake wetland, China

Spatiotemporal distribution of migratory birds in relation to phenological changes in wetland vegetation is significant in studying various ecological issues. In this study, SPOT-VGT imagery was used to monitor vegetation cover change in the Poyang Lake wetland. The Normalized Difference Vegetation Index (NDVI) served as an indicator to reveal vegetation change of the wetland. Spatiotemporal trends of the NDVI time series and distribution of migratory birds in the wetland from 1999 to 2009 were investigated. Migratory birds were classified based on their feeding guilds. The correlation coefficients between a time series of NDVI and different types of migratory birds were obtained. sults show: (1) The inter-annual NDVI shows an uneven yet increasing trend since 2000, with the average NDVI ranging between 0.17 and 0.64. Its seasonal change is roughly in line with the seasonal variability of natural vegetative growth in the area. (2) Both the number of species present and the population of migratory birds show an increasing trend, and avian biodiversity has greatly increased. In most years herbivorous birds dominated over other foraging guilds. (3) The correlation between NDVI variability and bird population, usually above 0.5 in typical reservation zones, differs in reservation zones and for foraging guilds of migratory birds. NDVI was significantly correlated with the population of herbivorous birds. (4) Land-use types can influence this correlation through its reflection of different NDVIs. Wetland is positively correlated with bird population of all species, while cropland is negatively correlated.