Suitable overwintering habitat simulation and the drivers of their population expansion for Siberian cranes (Grus leucogeranus) in China.

To gain a more comprehensive understanding of habitat preferences, potential wintering area distribution and drivers of population expansion of Grus leucogeranus, we selected 70 geographical distribution points and 11 environmental variables in its wintering period from 2015-2022. We modeled suitable habitat patterns for G. leucogeranus in China using MaxEnt model, and analyzed the relationship between suitable habitat distribution and environmental factors. The results showed that the dominant factors affecting the overwintering distribution of G. leucogeranus were distance to mudflats, elevation, average precipitation in February, distance to water sources, minimum temperature in December, and land use type, with a cumulative contribution rate of 94.6%. The wintering ground of G. leucogeranus in China was mainly distributed in the middle and lower reaches of the Yangtze Plain and the Yellow River Delta of the North China Plain. In these regions, the area of high-, medium- and low-suitability habitat were 17685, 60787 and 60747 km2, respectively. A total of 40 protected areas had been established in the high-suitability wintering range of G. leucogeranus in China, whereas 12 high-suitability wetlands such as Qili Lake in Anhui, Liangzi Lake in Hubei and Chenjia Lake in Jiangxi were still unprotected. The wintering grounds had shown a trend of expansion to the northeast and southeast since 2015. Considering the large-scale habitat shifts of G. leucogeranus in recent years and the frequent new wintering records in various places, we suggested that the shortage of food resources in natural habitats was the main factor driving the expansion of G. leucogeranus' wintering range. To protect G. leucogeranus more effectively, we should strengthen the restoration of natural habitats and the management of farmland habitats.

Population sizes and group characteristics of Siberian Crane (Leuco-geranus leucogeranus) and Hooded Crane (Grus monacha) in Poyang Lake Wetland.

Both the Siberian Crane (Leucogeranus leucogeranus) and Hooded Crane (Grus monacha) have limited population sizes and are considered endangered by domestic Chinese and international agencies. To document the current size of their respective populations and characterize their groups, between October 2012 and April 2013 we undertook fieldwork at four nature reserve areas within the Poyang Lake wetlands. We divided Poyanghu National Nature Reserve (PYH) into the Wucheng (PWC) and Hengfeng areas (PHF), because each are each located in different counties. Our fieldwork showed that the Siberian Crane occurred mainly in PYH (364 in the PHF, 158 in the PWC) and the Nanjishan Wetland National Nature Reserve (NJS, with 200 individuals). The Hooded Crane was mainly distributed in PYH (302 in the PHF and 154 in the PWC). Family groups accounted for more than 50% of the total number of groups among both species, with Hooded Cranes forming more family groups than Siberian Cranes. Typically, these groups were formed of two adults with one offspring (Siberian Crane), and two adults with two offspring (Hooded Crane), with the mean family group size of the Siberian Crane and Hooded Crane being respectively 2.65 ± 0.53 (n=43) and 3.09 ± 0.86 (n=47) individuals per group. The mean collective group size of the Siberian Crane and Hooded Crane included 28.09 ± 24.94 (n=23) and 28.94 ± 27.97 (n=16) individuals per group, respectively, with the proportion of juveniles among Hooded Cranes being more than double that seen among the Siberian Cranes.