We have a nursery roost with two kinds of bat in the farmhouse roof and do a count for the National Bat Monitoring Programme twice a year. Pipistrelles are those you normally see at dusk and will leave the roost over the space of about half-an-hour. They are long-lived and tend to have their favourite "patrol" area - one will circle the pond, one fly above the muck heap, another fly through the hay barn and so on, before going down to the stream to feed on midges and moths. The numbers plummeted after two very cold, wet Springs in 2011 and '12 but last year's warm summer saw a small improvement.