Recent climate change is recognized as a main cause of shifts in geographical
distributions of species. The impacts of climate change may be aggravated by habitat
fragmentation, causing regional or large scale extinctions. However, we propose that climate
change also may diminish the effects of fragmentation by enhancing flight behaviour
and dispersal of ectothermic species like butterflies. We show that under weather conditions
associated with anticipated climate change, behavioural components of dispersal of
butterflies are enhanced, and colonization frequencies increase. In a field study, we
recorded flight behaviour and mobility of four butterfly species: two habitat generalists
(Coenonympha pamphilus; Maniola jurtina) and two specialists (Melitaea athalia;
Plebejus argus), under different weather conditions. Flying bout duration generally
increased with temperature and decreased with cloudiness. Proportion of time spent flying
decreased with cloudiness. Net displacement generally increased with temperature. When
butterflies fly longer, start flying more readily and fly over longer distances, we expect
dispersal propensity to increase. Monitoring data showed that colonization frequencies
moreover increased with temperature and radiation and decreased with cloudiness.
Increased dispersal propensity at local scale might therefore lower the impact of habitat
fragmentation on the distribution at a regional scale. Synergetic effects of climate change
and habitat fragmentation on population dynamics and species distributions might therefore
appear to be more complex than previously assumed.