Common noctule

Look up while the sky is still bright. The noctule is one of Britain's largest bats, with a wingspan of up to 40 cm, and it hunts in the open, often well above the treetops, flying high and fast with steep dives after insects. It forages mainly at dusk, so it is the bat to watch for over meadows, lakes and parkland before the smaller species take over. Its calls run from about 20 to 45 kHz and peak near 25 kHz, low enough that some adults and children can hear them unaided. Set a detector low and the noctule's loud, spaced-out calls stand apart from the rapid patter of a pipistrelle.