Migration routes and adult survival of the critically endangered yellow-breasted bunting Emberiza aureola.

Migratory animals rely on multiple sites during their annual cycles. Deteriorating conditions at any site can have population-level consequences, with long-distance migrants seen as especially susceptible to such changes. Reduced adult survival caused by persecution at non-breeding sites has been suggested a major reason for the catastrophic decline of a formerly abundant, long-distance migratory songbird, the Yellow-breasted Bunting Emberiza aureola. However, it is unknown whether the ongoing extinction of this Eurasian species especially in the west of its range could be related to differences in survival or migration routes. We investigated survival rates of populations from both western and eastern parts of the breeding range and successfully tracked the migration of individuals from two eastern populations with light-level geolocators. We found moderate apparent local survival rates in eastern populations, but observed no returning birds in western populations. Our tracking data highlights (1) a joint migration corridor of eastern populations through eastern China, (2) long autumn stopovers likely used for moult and re-fuelling, and (3) very long occurrences at wintering sites. These areas should be given priority for future conservation measures. We call for an increased monitoring of adult survival and breeding output in multiple populations (including western ones) of this critically endangered species to determine (1) the causes for the observed differences in apparent local survival and (2) whether the current survival rates are sufficient to sustain viable breeding populations.