Snakes are the principal nest predators of the threatened reed parrotbill in a coastal wetland of eastern China

Nest predation is a major limiting factor of bird reproductive success, and predation by snakes may have particularly adverse effects on passerines. The reed parrotbill (Paradoxornis heudei) is a threatened passerine that inhabits reedbeds in East China, where it faces the risk of population decline due to habitat loss and degradation. Studies on the nest predation of this species are lacking. In this study, we monitored reed parrotbill nests in the core area of the Yancheng Nature Reserve, Jiangsu Province, China. We tracked the final fate of each nest and determined the identity of the predators using infrared cameras. We monitored a total of 13 and 15 active nests in 2017 and 2019, respectively, but only 5 nests were successful. Nest predation was responsible for 22 of 23 nest failures (95.7%). Snakes were the principal predators of the nests, responsible for 19 predation events (86.4%). We used abandoned reed parrotbill nests and quail eggs to create artificial nests. However, the survival rate of the artificial nests (63.3%) was significantly higher than that of the natural nests (11.3%), and rats replaced snakes as the principal predators. The best model indicated that the daily survival rate of reed parrotbill nests decreased with nest age. Our findings suggest that severe snake predation may be an important factor threatening populations of the reed parrotbill, even though the wetland habitat is well protected. The identification of specific nest predators may facilitate the conservation of this near-threatened bird through the development of effective management strategies in reserves. More studies on population estimates of the reed parrotbill and the interactions between this endangered bird and snakes using natural (rather than artificial) nests in different areas are needed. Keywords: Nest predation, Snake, Paradoxornis heudei, Threatened bird, Elaphe anomala