The significant correlation between the maximum number of red-crowned crane in the YNR and 5 climate variables within 10 years. F1, mean minimum air temperature in December 2 years earlier; F2, mean minimum air temperature in January of the following year 4 years earlier; F3, mean minimum air temperature in January of the following year 6 years earlier; F4, mean air temperature in January of the following year 6 years earlier; F5, precipitation in January of the following year 7 years earlier.