Mitigating Effects of Nest Structure on Predation Risk in Hainan Partridge (Arborophila ardens).

Nest predation is the primary factor contributing to breeding failure, particularly in tropical regions. Enclosed nest structures can disrupt predator search efficiency and reduce predation risk. However, their effectiveness varies with environmental conditions. In this study, we tested whether the arched covering structure of Hainan Partridge (Arborophila ardens) nests reduces predation risk by disrupting predator search efficiency, and compared the difference in artificial nest predation between the interior and exterior of the national park. To evaluate this, we conducted artificial nest experiments with camera trapping from April to June 2025 across four breeding sites located both inside and outside the National Park of Hainan Tropical Rainforest on Hainan Island, south China. We deployed a total of 204 artificial nests containing domestic pigeon eggs, comprising equal numbers of covered nests designed to mimic the nest structure of the Hainan Partridge and uncovered control nests. Results showed that the predation rate in the uncovered group was significantly higher than that in the covered group (62.75% vs. 46.08%, χ 2 = 5.711, p = 0.017). However, covered nests exhibited varying degrees of anti-predation effects within and outside the National Park of Hainan Tropical Rainforest. The primary predators were birds (Silver Pheasants Lophura nycthemera, Indochinese Green Magpies Cissa hypoleuca) and rodents (in the family Muridae), followed by other mammalian predators (Wild Boars Sus scrofa, Rhesus Monkeys Macaca mulatta, Chinese Ferret-badgers Melogale moschata) and reptiles (Common Water Monitors Varanus salvator). These findings highlight the functional limitations of nest-structure evolution within complex predation environments. Through comparisons between the interior and exterior of the national park, we also reveal the impact of conservation management on nest predation risk in tropical pheasants, providing critical insights into the trade-offs between reproductive strategies and survival pressures in tropical pheasants.