Studying the migration and the ecology of a high-Alpine long-distance migratory bird

Wheatears breeding in Switzerland have short migration distances compared to conspecifics breeding further north and face unpredictable conditions (e.g., snow melt) at their Alpine habitat in spring. We aim at describing in this population A) the movement throughout the annual cycle and B) measure how plastic birds can respond in their breeding and foraging behavior to the variation in the environment by switching micro-habitats. Our data inform on both local and global scale movements, providing new insights into migratory behavior and will allow a comparison with other wheatear populations.

We monitored a population of about 60 breeding pairs, each individually marked with color rings, throughout the reproductive seasons since 2014 in Val Piora, Ticino. We mapped territories, reported breeding progress and success weekly, and documented the preference for different foraging habitats. We tracked subsamples of individuals using “geolocators and pressure sensitive tags” between breeding seasons. Tags recovered the following year provided data for estimating the position, flight schedule, flight height, and altitudinal movement of the birds throughout the entire non-breeding season.

Our knowledge on the ecological needs in birds migrating long-distances is often limited to the breeding range. However, migrants are exposed to different environments during the annual cycle and their needs might differ between sites and along their migratory routes. The Northern Wheatear commutes between high mountain habitat and the Sahel zone, whereboth habitats are particularly vulnerable to environmental change. This is a good example for identifying how the birds interact with these environments, and how they balance their needs throughout the annual cycle.

Our data inform on the broad-scale movement patterns of Alpine Northern Wheatears, with migration routes across the Mediterranean Sea, migratory flights up to 5000 m asl, and non-breeding sites in the western Sahel. Futhermore, pressure data reveal new insight on regular diel altitudinal movements between breeding territories and roosting sites and at regional scale in response to local meteorological conditions during the pre-breeding period. Observation on the foraging behavior also highlighted the importance of micro-habitat heterogeneity as a crucial factor to prey accessibility.

• Valentin Amrhein, Department of Environmental Sciences, Zoology
• Dan Chamberlain and Martha Maria Sander, Department of Life Sciences and Systems Biology
• Martin Buchmann
• Heiko Schmaljohann, Institut für Biologie und Umweltwissenschaften
• Debora Arlt, Department of Ecology, Swedish University of Agricultural Sciences
• Tomas Pärt, Department of Ecology, Swedish University of Agricultural Sciences
• Herman van Oosten, Herman van Oosten, Oenanthe Ecologie
• Cas Eikenaar, Institute of Avian Research “Vogelwarte Helgoland”

• The Swiss Federal Office for the Environment contributed financial support for the development of the data loggers (UTF-grant no. 254, 332, 363, 400).