2.1 Study species and working sites
The Kentish plover breeds in the northeast coast and inland saline lakes in Eurasia, while the white-faced plover is confined to the southeast coast and islands in China . We selected a white-faced plover population on Paisha Island (20° 54ʹ N, 110° 29ʹ E, PI) in a subtropical climate. We also used three Kentish plover populations: one in a north temperate coastal area at Bohai Bay (39° 14ʹ N, 118° 52ʹ E, BB), another in a desert inland lake at Taitema Lake (39° 26ʹ N, 88° 12ʹ E, TL), and the last one in an alpine inland lake habitat at Qinghai Lake (36° 48ʹ N, 100° 45ʹ E, QL). Ambient temperature was highest in the PI population, followed by BB and TL, and was lowest in the QL population (Figure 1). The distribution of these populations provides a good study system for understanding how ambient environment variance modulates local sexual selection. Both species exhibit biparental care, and extra-pair paternity rates are typically low (0-4.1%, ), suggesting potentially post-copulatory mate choice based on male incubation behavior. Fieldwork was conducted during the breeding seasons in 2018 and 2019, with work on Paisha Island and Bohai Bay conducted from May to June, work at Qinghai Lake from May to July, and work at Taitema Lake conducted from May to July in 2019.