The great cormorant Phalacrocorax carbo (Linnaeus, 1758) can create significant conflicts with fisheries as a result of removing significant fish biomass. This is exacerbated by recent population increase in most of Europe. This study uses long-term census, climate, and environmental data to explore the wintering dynamics and strategies of the species. In Turkey, the total overwintering population, population density, and distribution of cormorants have increased significantly. Correlations with different climatic accounted for 20% to 56% of the variation in the total number of overwintering cormorants. The total number of cormorants overwintering was positively affected by warmer weather conditions in autumn and negatively by increased snow cover in winter. The Principal component analysis identified attraction (At) and avoidance (Av) factors, a two-component solution involving 12 climate variables for choosing the wintering sites of cormorants, that explained 84.3% of the total variance in total number of overwintering cormorants. Linear regression using the scores of the At/Av climate factors predicted 59.0% of the total number of overwintering birds. Our study also demonstrates that long-term census data with both resident and winter migrant populations during the winter can be used to estimate the resident population size of the species.