Bat Roosts in Trees
Ground and Aerial Assessments and Activity Surveys of Trees
Introduction
All UK bat species, with the exception of horseshoe bats, have been found to utilise natural roost features within trees at some point in their life cycle. Mature trees are more likely to possess the types of features that bats will use, but any tree could be used if there is a suitable roosting feature, such as loose bark, splits, holes and cracks.
The NPTC certified tree climbers from Echoes Ecology, who also hold Scottish Natural Heritage bat licences, regularly carry out ground and aerial inspections of trees, looking for evidence of roosting bats. Whenever a feature cannot be fully inspected, activity surveys are completed. Four examples of tree roosts discovered in 2017 are described below.
Sweet Chestnut
A mature sweet chestnut (Castanea sativa), which was due to undergo health and safety works, was inspected from a Mobile Elevated Work Platform (MEWP) and an east-facing woodpecker hole was found to contain a single roosting pipistrelle (Pipistrellus sp.).
Aspen
During the ground inspection of an aspen (Populus tremula) tree stump in the Highlands, a single pipistrelle was seen roosting underneath the loose bark.
Silver Birch
Another bat was found in the Highlands roosting in a rot-hole within a silver birch (Betula pendula) during an aerial inspection using an endoscope. The bat species could not be identified due to its position in the roost.
Silver Birch
A silver birch could not be climbed due to health and safety reasons and so the potential roost feature could not be fully inspected. Two activity surveys were completed and during a dawn survey in July, one Myotis species of bat entered a hole in a stem 4 metres above the ground.
Outcomes
Ground inspections, aerial inspections and activity surveys all prove to be successful survey techniques for identifying bat roosts in trees. The skills held by the Echoes Ecology team ensure that all survey methods are available, allowing the appropriate method to be selected for the potential roost feature in question. This ensures valuable data can be gathered to inform a robust report on the presence of bat roosts within the survey sites and allows for the successful application for Habitats Regulations licences.