Learning bird song is straightforward enough: go outside, listen to birds. Then watch birds. Start to put the senses together. Which bird says what? That sweet, happy-yet-wistful song any time of year is a robin, that harsh screech a jay, the strident chiff-chaff-chiff-chaff in March is – guess what – and the gentle hueets moving through a low tree canopy six months later are contact calls from the same species. Birds are only a part of nature’s soundscape, though. They’re often the dominant one, but it depends on where in the world and when in the day or year you happen to be listening.
At night, it’s often other creatures that rule the acoustic roost, inhabiting a secret world of sound that can be a little trickier to unlock. That might be because it’s a sound world predominately outside of human hearing range, as for super-squeaky bats. Fortunately, access to their secrets can be bought with a little help from a bat box, which I and the other Reading staff and students on the recent Devon field course very much enjoyed playing with. We started one evening by lying in wait for a roost of lesser horseshoe bats, which use very high frequency sonar they amplify through strange, leaf-like appendages on their nose. The sound is fantastical, an almost machine-like wavering whistle that is markedly alien. Making more conventional rapid clicking sounds were diminutive pipistrelle bats, accompanied by near identical soprano pipistrelles – a separate species mostly told by its higher frequency calls.