Migration phenology

More than 2 billion passerines migrate from their European breeding grounds to their residence areas in sub-Saharan Africa. The bird’s behaviour and migratory pattern is shaped by the seasonal food availability en route and in the African residence areas, as well as by the short term weather conditions. The critical factors for a successful return to the breeding grounds are barely known for most species and populations of trans-Sahara migrants.

Therefore, we aim at answering the following quesionts:

• What are the temporal and spatial patterns of migration and residency for trans-Sahara migrants during the non-breeding period?
• What is the influence of seasonality of environmental factors on these patterns and their variability?
• How much are environmental factors in the African residence areas responsible for reproductive success?
• Are populations with high connectivity between breeding and non-breeding ranges more affected by local environmental conditions in the African residence area than those with low connectivity?

For selected populations, their African residence areas and to some extent their migratory routes and stopover sites are identified by using miniaturized geolocator. This allows investigating the impact of environmental conditions on the timing and spatial patterns during the non-breeding period. In addition, it enables the investigation of habitat use.

Comparing the relationship between environmental factors en route and the African residence areas with the breeding success will allow extracting the most relevant factors governing species- and population-specific migratory strategies. In addition, looking at kinship will shed light on the pheno- and genotypic variability in migratory patterns.

These questions are being investigated in hoopoes, Alpine swifts and wheatears. Several other species are similarly studied in cooperation with international partners. Significance

The degree of flexibility in migratory patterns in relation to environmental conditions allows for estimating the potential and the limits of phenotypic plasticity, and thus the potential capacity to adapt to fast environmental changes, which can affect reproduction.

To learn more about these dynamic processes is fundamental for our understanding of bird migration, but can also be crucial for species-specific conservation measures.