Flyway-scale lead and multielement exposure in globally threatened Cinereous vultures (Aegypius monachus) wintering on the Korean Peninsula: Insights from tissue burdens and stable lead isotopes.

Lead (Pb) is a major toxicant in avian scavengers, but its ecological role and exposure pathways along the East Asian flyway remain unclear. Immature Cinereous vultures (Aegypius monachus) migrate from Mongolia through China to winter on the Korean Peninsula, where they mostly congregate near the Korean Demilitarized Zone (DMZ), creating a potential flyway-scale bottleneck where local hazards may affect much of the population. This study investigates Pb and multielement exposure in 74 immature vultures recovered near the DMZ by quantifying Pb concentrations in liver and muscle, measuring hepatic Cd, Cu, Zn, Ni, As, V, and Fe, and analyzing stable Pb isotope ratios (206Pb/207Pb, 208Pb/206Pb, 208Pb/207Pb) in tissues to assess potential exposure sources. Hepatic Pb concentrations ranged from 1.17 to 33.4 μg/g dw, and 16.2% of individuals reached levels consistent with Pb-induced mortality. Hepatic Pb burdens did not differ among probable causes of death (gunshot, trauma, emaciation, electrocution, suspected poisoning, and unknown), indicating pervasive Pb exposure across the wintering cohort. Muscle Pb concentrations were generally low, except in one gunshot-injured bird, which had an extreme level of 120.9 μg/g dw. In contrast, other hepatic elements showed comparatively moderate concentrations, identifying Pb as the primary toxicological concern. Tissue Pb isotope signatures overlapped with ammunition-related and other anthropogenic Pb sources, supporting a mixed-source exposure scenario in which Pb-based ammunition likely contributes. These findings indicate that immature Cinereous vultures wintering on the Korean Peninsula are widely and persistently exposed to Pb, highlighting the need for flyway-scale monitoring and targeted mitigation across the Mongolia-China-Korea flyway.