Flexible navigation response in common cuckoos Cuculus canorus displaced experimentally during migration

Abstract

The complex innate spatio-temporal migration programs, capable of guiding migrant species thousands of kilometers, represents an evolutionary trade-off between species-specific resource needs and movement-related risks, resulting in varying migratory patterns across species and populations1,2. The navigational basis of this program is still an unsolved mystery despite decades of research3. To investigate the navigational capabilities in birds, experimental displacement is a common practice4. Experienced songbird migrants can perform true navigation involving the use of a map sense to identify the position of the current location in relation to a goal, enabling them to compensate for a displacement, even outside familiar areas5. This has been documented using various methods based on migration directions of displaced birds, such as ring recoveries6,7, radio tracking8,9, and orientation cages10–12. However, the actual movement paths are critical to understand the processes of navigation3 and only recent development of remote tracking technologies has made this now possible13. We investigate the navigational capabilities in experienced individuals of a solitary, nocturnal migrant by experimentally displacing adult common cuckoos, a long-distance migrant with one of the most complex migrations known, using seven different staging sites between each breeding season14. Immediately before the usual start of post-breeding migration, we displaced 12 birds from breeding grounds in northern Europe (Denmark) more than 2500 km to south-westernmost Europe (Spain), over 1000 km from the route normally followed by cuckoos breeding in Denmark (Fig. 1A).