From northern Europe to Ethiopia: long-distance migration of Common Cranes (Grus grus)

摘要

The majority of Common Cranes (Grus grus) breeding in northern Europe are short- to medium-distance migrants that overwinter in southern Europe, northern Africa, and the Middle East. However, some individuals migrate longer distances to as far as Ethiopia. Using data from 18 satellite-tracked juvenile Common Cranes, we assessed (1) the length and landscape composition of the migratory routes used and (2) the behaviour of neighbouring Finnish and Estonian (500 km apart in the north-south direction) sub-populations. Our results show that Common Cranes mainly use the East European flyway to reach the wintering grounds in Ethiopia, yet some individual cranes may alternatively use the Baltic-Hungarian migration route. Neither duration nor the number of stopovers used influenced the flight distances of the cranes. Further, 7-19 days of refuelling enabled the cranes to cover long flight distances, from 2,420 to 5,110 km in 6-15 days, without the need for settling down at potential stopovers on the route. Contrary to our expectations, the main refuelling sites of the Finnish breeding population were further south (in southern Ukraine) than those of the Estonian population (in Belarus). Despite the longer flight distances, Finnish cranes used three main migration stages, while cranes breeding at more southern sites generally used mainly four stages. Our findings demonstrate that large-sized social migrants such as the Common Crane may have spatially segregated, flexible migration patterns that involve only a few carefully selected stopovers during long-distance migration.