Effectiveness of territorial protection categories in conserving an endemic island bird during population fluctuation

Abstract Protected areas represent cornerstones of biodiversity conservation on oceanic islands, yet their effectiveness for endemic species remains poorly evaluated. We assessed how various territorial protection categories conserve an endemic oceanic bird by comparing periods of population maxima and minima in Fuerteventura. Using 500‐m transects across the island, we analyzed local abundance differences inside versus outside protected areas, identified proportions of populations within protection boundaries, and examined cohabitation patterns with other avian species. Local stonechat abundance was significantly higher only inside Special Areas of Conservation (SACs) (non‐targeted to birds), with no advantage in Special Protection Areas for Birds (SPAs), despite their avian conservation purpose (i.e., targeted to birds). Temporal analyses revealed a sharper decline in stonechat abundance inside SACs compared to unprotected areas, and similar changes outside and inside SPAs. Approximately 42% of the stonechat population and 72% of its occupancy area remained outside SPA boundaries during both periods, demonstrating inefficient spatial alignment with the species' distribution. Unprotected areas gained critical significance during the 2024 population minimum, as static boundaries failed to capture the species' shifting distribution patterns. The stonechat showed positive associations with five other endemic subspecies but no spatial overlap with emblematic “flagship” species that typically drive conservation decisions. Conservation planning must adopt more dynamic approaches that not only account for species' spatial distributions under optimal conditions but also identify and protect key refugia during population declines. This is particularly critical for improving the effectiveness of protected areas for island endemics with restricted and environmentally sensitive habitat requirements.