This species feeds principally over open calm water, particularly canals, rivers and lakes, on small emerging and emergent insects, often taken from the water surface. It prefers water lined by open rough vegetation without trees. Most of the known summer maternity roosts are in buildings, often in large attics and church steeples, in groups of 40-600. Some tree and bat box roosts are recorded. It frequently hibernates in underground habitats ranging from natural caves to cellars and bunkers. It is a partial migrant, with winter and summer roosts often separated by more than 100 km (maximum recorded: 350 km, and it may need good habitat links between summer and winter roosts.