This study analyzed the relationship between environmental factors and the temporal changes of the bird populations
during the every January from 1999 to 2016 (18 years) in Donglim reservoir. 'Winter Waterbird Census of Korea' data
by National Institute of Biological Resources were used for the bird population data, and principal component
analysis and cluster analysis were used to analyze the changes of annual population. The average temperature of
January and the average storage rate of the reservoir were used as environmental factors. According to the results of
the study, the population changes in the study area can be explained by the increase and decrease of two water bird
groups and a mountain bird group. The average temperature of the years when the population of water bird groups
increased was more than 1.4℃ in comparison with the year when mountain birds increased. On the other hand, the
influence of the water content was not clear. The visiting of Baikal Teal affected by temperature was a factor affecting
the other group of water bird and a mountain bird group. The results of this study suggest that the temperature
change affects the global spatial distribution of birds and the migration of large population species such as Baikal Teal
affects species composition and populations of birds at local scale. Therefore, understanding of environmental
changes at large scale and spatial distribution of species and flock contributes to understand the temporal variation of
the bird population at regional or local scales.