Introduction
The influence of light pollution was already considered by CMS as a problem, mainly for night time migratory birds but also for bats. Three main areas were identified:

1. Interaction with feeding activity, including prey distribution and intra bat species competition;
2. (In)direct effects on roosts;
3. Effects on commuting - all non-feeding related movements, including barrier function of lit roads and fragmentation of the night landscape.

This IWG was established during the AC12 Meeting in Budapest with the following objectives:

• Create an assessment of the different aspects of impact of light on the various bat species;
• Create methodological guidelines to survey the effect of light pollution (experimental design of studies) and
• Conservation guidelines (case specific).