Migration behaviour and annual energy budgets in a short-distance migrant

In this study, we aim at describing individual-level migration behaviour and performance of Starlings from different European breeding populations with respect to migration routes and timing, stopover, moulting, and wintering sites, flight characteristics, and diel behavioural patterns. We are specifically interested in measuring and comparing annual energy expenditure for individuals with different migration strategies, wintering sites, and reproductive success.

Throughout the breeding season we monitor and follow reproductive success of Starlings in multiple nest box populations where we capture and mark adult birds as well as their nestlings. This allows us to identify individual birds in a population and follow their breeding success from one year to another. Each year we track a subsample of adult birds using state-of-the-art multi-sensor geolocators to gather detailed information on their migration behaviour. Additionally, we collect feather samples from all breeders allowing us to identify their moulting sites via stable isotope techniques.

Throughout the annual cycle migratory species need to balance energetically demanding events like breeding, moult, and migration. To avoid energy allocation conflicts, these events are often separated in time and space. Measuring energy expenditure in free-ranging birds across the annual cycle, however, can be challenging. Therefore, energetic requirements and expenditure, and their causal nexus at various annual phases remain a highly debated but hitherto little-studied area in bird migration research, particularly in free-ranging passerine migrants.

First project results showed that Starlings from North European exhibit a mixed migration strategy where part of the population engage in moult migration in early summer just after the breeding while others remain near the breeding sites until late autumn. Interestingly, multi-sensor tracking revealed that Starlings predominantly migrate at night with individual flight bouts regularly exceeding 12 h and birds flying as high as 2500 m above sea level. Broad-scale phenology data revealed that Starlings are advancing their spring migration timing but not fast enough to cope with climate change.

• Oskars Keišs, University of Latvia, Institute of Biology
• Stephanie Kramer-Schadt, Leibniz Institute for Zoo and Wildlife Research
• Morrison Pot, Netherlands Institute of Ecology (NIOO-KNAW)
• Manfred Hug
• Peter Tamm