The white-naped crane (Grus vipio) is listed as a vulnerable species by the IUCN. The western population of white-naped cranes continues to decline. In 2017 and 2018, we fitted 50 individuals from the western population with GPS-GSM satellite transmitters in eastern Mongolia. From July 2017 to May 2019, we obtained 48 migration routes in spring and autumn, respectively. We found that during migrations, 91.67% (spring) and 72.91% (autumn) of tracked individuals chose the Luan River upper reaches (Guyuan-Zhenglanqi-Duolun) as their stopover site, where they stayed for 36.16 ± 15.00 days (75%) in the spring, and 20.26 ± 11.08 days (67%) in the autumn. Habitat selection model showed that water (specifically distance to lake) was the main environmental variable which affects the migration route choice for white-naped cranes. The cranes preferred the stopover site that was close to lake (< 210 km) and had gentle slopes (< 1°) at an altitude between 1,200-1,500 m. The Luan River upper reaches was close to river (< 70

BackgroundThe great bustard (Otis tarda) holds the distinction of the heaviest bird to undergo migration as well as the greatest degree of sexual size dimorphism among living birds. Though the migration of the species has been widely discussed in the literature, researchers know little about the migration patterns of the subspecies in Asia (Otis tarda dybowskii), especially the males. MethodsIn 2018 and 2019, we captured six O. t. dybowskii ( ve males and one female) at their breeding sites in eastern Mongolia and tagged them with GPS-GSM satellite transmitters. This constitutes the rst time that male great bustards of the eastern subspecies have been tracked. We combined the tracking data of our only female with other three females from central Mongolia, which was published in previous study for analysis. ResultsWe found notable differences between the sexes: 1) males started migration later but arrived early than females in the spring, but not in autumn; 2) males had 1/3 of the migration duration of females (16.44 ± 14.68 days vs. 49.34 ± 21.28 days); 3) males migrated about 1/2 the distance of females (945.13 ± 79.00 km vs. 1922.88 ± 87.08 km). Additionally, we found bustards exhibited high delity to their breeding, postbreeding and wintering sites. Indeed, most of the wintering sites found by GPS tracking in this study were also utilized 70 years earlier, according to previous work. For conservation, we found only 22.20% of GPS location xes of bustards were within protected areas and less than 5.0% for wintering sites and during migration. ConclusionsOur ndings suggest that the migration patterns of eastern great bustards are sex-speci c and more conservation effort is needed for the Asian populations of this threatened species.

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Background The great bustard (Otis tarda) holds the distinction of the heaviest bird to undergo migration as well as the greatest degree of sexual size dimorphism among living birds. Though the migration of the species has been widely discussed in the literature, researchers know little about the migration patterns of the subspecies in Asia (Otis tarda dybowskii), especially the males. Methods In 2018 and 2019, we captured six O. t. dybowskii (five males and one female) at their breeding sites in eastern Mongolia and tagged them with GPS-GSM satellite transmitters. This constitutes the first time that male great bustards of the eastern subspecies have been tracked. We combined the tracking data of our only female with other three females from central Mongolia, which was published in previous study for analysis. Results We found notable differences between the sexes: 1) males started migration later but arrived early than females in the spring, but not in autumn; 2) males had 1/3 of the migration duration of females (16.44 ± 14.68 days vs. 49.34 ± 21.28 days); 3) males migrated about 1/2 the distance of females (945.13 ± 79.00 km vs. 1922.88 ± 87.08 km). Additionally, we found bustards exhibited high fidelity to their breeding, post-breeding and wintering sites. Indeed, most of the wintering sites found by GPS tracking in this study were also utilized 70 years earlier, according to previous work. For conservation, we found only 22.20% of GPS location fixes of bustards were within protected areas and less than 5.0% for wintering sites and during migration. Conclusions Our findings suggest that the migration patterns of eastern great bustards are sex-specific and more conservation effort is needed for the Asian populations of this threatened species.