Case Report of Plastic String Entanglement Mortality in a Breeding Oriental Reed Warbler.

Rapid economic development and urbanization have exerted considerable impacts on the environment and wildlife. Species that survive and establish populations in new environments benefit from abundant food resources and reduced predation pressure; however, they are also exposed to certain risks. Plastic production and use have increased markedly alongside population growth and urbanization, with large quantities of plastic products entering ecological environments. Whereas birds and other animals use them as nesting materials, plastic nesting materials pose toxicity and entanglement risks, affecting bird survival and reproduction. In addition, although numerous studies have reported cases of avian mortality due to entanglement, such studies have predominantly focused on medium to large species (mostly seabirds) and nestlings. This study documents a case observed on June 28, 2025, in the Baiyangdian Wetland, Hebei Province, China, where an adult breeding Oriental Reed Warbler parent bird died due to entanglement in plastic string present in its nesting material. The nest contained one unhatched egg, and another parent bird was observed maintaining vigilance near the nest. No subsequent egg-laying was observed, suggesting that the deceased parent was likely female and that the breeding attempt failed. Subsequently, the nest status was photographed and documented. Based on local conditions, the plastic string probably originated from fishing equipment or reed-weaving. This case directly demonstrates the hazards that plastic products pose to avian survival and reproduction.