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, Eurasian, longdistance migratory songbird, the Yellow-breasted Bunting Emberiza aureola. However, it is unknown whether the extinction of the species in the west of its range could be related to differences in migration routes. We investigated survival rates and migration routes of populations from both western and eastern parts of the breeding range. We found moderate apparent 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 non-breeding sites. These areas should be given priority for future conservation measures. The lack of returning individuals in the western populations could hint at reduced survival rates due to additional pressures as a consequence of their potentially longer migration route or lower breeding site fidelity.

AbstractLittle is known on the migration routes of songbirds breeding in Siberia. We used satellite transmitters to study the migration of two White´s Thrushes Zoothera aurea captured during breeding season in the Ural Mountains, Russia. One of the devices transmitted during spring and the breeding season (May to September) in the following year from the Khangai Mountains of central Mongolia, 3000 km southeast of its former breeding season site. Based on the combination of lack of accurate locations, potentially unsuitable habitat, unusual behaviour, and unusual location outside of the known breeding range we consider it most likely that the bird died there during migration, while the transmitter continued to function. No data on migration routes or non-breeding areas were received, although the movement to Mongolia suggest a migration route east of the Qinghai-Tibetan plateau.

A document by Wieland Heim. Click on the document to view its contents.