Breeding Ecology of the Critically Endangered Baer's Pochard (Aythya baeri): Nest Threats and Conservation Implications.

Baer's Pochard (Aythya baeri), a diving duck endemic to eastern Asia, has once experienced a significant population decline and was classified as "Critically Endangered" in 2012. However, the factors contributing to this decline remain poorly understood. Nest survival is a crucial demographic parameter that significantly influences avian population dynamics and is often correlated with various environmental factors and the breeding period. We conducted research on its breeding biology from 2019 to 2022, documenting a total of 108 nests with laying dates ranging from 25 April to 15 July. The nest success rate was 24.97%. Predation was the primary cause of nest failure, accounting for 44.66% of nest failures, followed by desertion (17.48%), flooding (7.77%), and egg collecting by local people (6.80%). The analysis of the factors affecting daily nest survival indicated that daily nest survival was positively correlated with the height above water and the distance to shore of mound where they nested, but negatively correlated with the laying date. We suggest that controlling nest predation, providing suitable nesting sites, and maintaining suitable water levels are crucial for ensuring the nesting success of Baer's Pochard.