Butterfly migration
Each autumn, large numbers of red admirals migrate throughout northern Europe, flying south, to reach areas with conditions suitable for surviving the winter. Even though red admirals are regarded as migratory, since they are only rarely found in the northernmost part of their distribution during winter, we still know very little about the actual migration routes. This is much due to the fact that tracking migratory movement of small animals with variable migration patterns, such as butterflies, is difficult with standard mark-recapture methods or genetic analysis.
In this project we have used stable hydrogen isotope measurements of wings from European red admirals (Vanessa atalanta) to study several aspects of this species’ migration. We have also observed the visible butterfly migration at Falsterbo peninsula, the southwesternmost point in Sweden, where red admirals are seen most autumns flying towards the Danish coast on their way to more southern parts of Europe.
This project is financed by grants from the Swedish Research Council and FORMAS to Susanne Åkesson.
The affect of wind
Weather parameters were used to analyse what factors are important for red admiral migration across the sea. Wind direction was one of those, affecting the initiation of the migratory departure. However, most other studies of butterfly migration have reported no large effect of wind direction, which is probably because the butterflies in our study were about to cross open sea for more than 20 km, whereas most previous studies were from inland locations where butterflies could avoid wind effects by flying close to the ground or on the lee side of topographical features. Photo: Erik Svensson- 1 of 3
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