Variation of migration routes in the central Asian-breeding Common Cuckoo population influenced by the Qinghai-Tibet Plateau

Ecological barriers present significant challenges to bird migration by limiting the availability of stopover sites and shelters. The Qinghai-Tibet Plateau, a major migratory barrier located in higher latitude Central Asia, exerts a substantial influence on avian migration patterns. Species traversing such ecological barriers may adopt multiple optimal routes, which can contribute to the formation of migratory divides. From 2018 to 2021, the migration routes of 13 adult Common Cuckoos (Cuculus canorus) breeding in the north of the Qinghai-Tibet Plateau were tracked using satellite transmitters. We found Common Cuckoos have two primary migration routes: western and eastern, respectively following western and eastern edges of the Qinghai-Tibet plateau. The eastern and western routes are likely the optimal routes for the Central Asian Common Cuckoos population to navigate the Qinghai-Tibet Plateau. Furthermore, two individuals exhibited intermediate migration routes, suggesting attempted traverses of the Qinghai-Tibet Plateau, although neither completed the migration. These intermediate routes may indicate migratory behavior influenced by hybridization between eastern and western populations or migratory flexibility. Common Cuckoos exhibit significantly faster migration speed, flight speed, and shorter stopover durations during spring compared to autumn. The observed seasonal differences in migration behavior support birds following time-minimization strategies during spring migration. These results revealed the diverse migration routes of Common Cuckoos shaped by the Qinghai-Tibet Plateau and seasonal variation in migration patterns.