Day surveys of potential roost structures Inspecting every building or structure (e.g. trees, bridges, barns, outhouses) likely to be inhabited by bats during the day is a time-consuming process. However, survey time can be reduced if roost preferences of individual species are taken into account. For instance, long-eared and lesser horseshoe bats show a marked preference for older buildings, while pipistrelles are commonly found in modern buildings. Daubenton’s bats are frequently found roosting underneath bridges, and noctule colonies are most frequently found in big trees. When surveying buildings, ask the householder first whether bats are known to be present. A negative response should be treated with some caution because, often, bats are present without the householder’s knowledge, but positive replies should always be followed up. Carefully survey the outside of the building for droppings, paying particular attention to sheltered areas such as window ledges or pipes where droppings can lie undisturbed. Cobwebs can often trap droppings and are always worth a close inspection. Scan the outside of the building for potential access points such as broken ventilation bricks or loose slates and look for droppings under these points (see also Hutson 1987, Search the loft space, although check with the householder first about safety and potential hazards (see Chapter 2). Gable ends and chimneys are often roosting points for pipistrelles and serotines, although long-eared bats can be found anywhere
along the roof ridge. Look for droppings and listen for squeaking or movement from between the tiles and felt on hot days. Bats have frequently been found drowned in open water tanks, so it is always worthwhile to check them. It is hard to locate tree roosts by day surveys because there are often no external signs of bat occupancy. One technique is to survey trees in winter when the foliage is not present and look for obvious holes. If large colonies use them in the 3.4 LOC ATION OF KEY SITES AND FEEDING AREAS 31 summer the wood maybe smoothed at the entrance. Brown staining from urine, faeces or fur rubbing can be present but often brown stains are connected with rot so their presence is not conclusive. Likely trees can be marked and revisited in the summer at sunset to watch for emerging bats. On hot days colonies are active and can be quite noisy so it is possible to walk through woods listening for the sounds of colonies. Walking through woodland an hour before sunrise during July and August can also reveal roosts (see Appendix 4).