The optimal survey season for manual bat detector surveys starts at the beginning of May and continues until September. While surveys for commuting and foraging bats can be undertaken from March/April onwards (BCT Guidelines/NRA Guidelines), surveys designed to also detect roosts, especially maternity roosts, should be restricted to the period May to September. As the presence of bat roosts on a proposed development site may have a significant bearing on the potential for the development of the site, it is important that this aspect of bat activity is covered in any manual bat detector survey. Therefore we recommend waiting until early May to conduct manual bat detector surveys.
Such surveys must be undertaken in suitable weather conditions with temperatures above 7C, little to no wind and no precipitation. Planning ahead for any potential bat surveys required is of the utmost importance as adverse weather conditions can delay the completion of surveys for long periods. In addition, where bats are found to be using a site, further survey work may need to be scheduled to ascertain the level of bat usage at the site and therefore planning initial surveys as early as possible in the survey season is advisable. This is especially the case in larger sites with a high proportion of suitable bat habitat such as buildings with roof cavities, caves, disused mines, mature trees, hedgerow and treeslines, watercourses or waterbodies and woodland.
Please contact us for further information on bat survey work carried out by McCarthy Keville O’Sullivan.