Sonogram analysis 3.4.7 Bat boxes The primary function of bat boxes is to provide artificial roost sites for bats, particularly in areas such as coniferous plantations where there is a shortage of natural sites. However, the provision of boxes also makes the bats easier to find, so that surveys of bats in woodland become possible. In continental Europe this has proved to be a particularly valuable technique for Bechstein’s bats, for which other survey techniques are inappropriate. Guidance on the setting-up of bat box schemes, including construction, siting and inspection, is given by Stebbings & Walsh (1991). The frequency with which the boxes are inspected will depend both on the need to check that the boxes are well sited and available to the bats, and the requirements of any research project. There is still much scope for experimentation with new designs. However, such projects are only useful if they produce results that allow comparison between different types of boxes or different situations. It is essential, therefore, that careful thought is given to the experimental design before the boxes are erected and that the location, type and subsequent usage of each box are carefully recorded. Large projects involving more than boxes are more likely to give statistically meaningful results than small projects with just 20 or 30 boxes and it may well be worthwhile for researchers to cooperate on projects.