Weighing about 30 g, the noctule is thought to be the biggest native bat species next to the greater mouse-eared bat. Characteristics are the velvet-like brownish fur, relatively short and broad ears and a mushroom-like lobe at the base of the ear. Long and narrow wings enable fast hunting flights in the open air. Like many migratory birds, noctules cover long distances between their summer roost areas and hibernaculums twice a year. Distances of more than 1,000 km are possible, for example from the northern part of Brandenburg to Switzerland. Most of the nursery roosts, where 20 to 50 females rear their young, are located in the north and northeast of Germany and Europe. Wintering areas are less well definable. During migration in April, May, and again starting at the end of August, large numbers of noctules become concentrated particularly along rivers. Here, riverine forests play an important role in providing roost sites and foraging grounds during migration