Bats roost in trees, caves, cavities or buildings. Loss of natural habitats has increased the importance of man-made structures for roosting bats. In fact all 17 breeding species of bat in the UK make use of buildings on occasion, although some species are more reliant on buildings than others.

Bats use a wide variety of places within buildings including spaces beneath roof tiles, between hanging tiles, behind fascia and barge boarding, soffits, sash windows, chimneys, loft spaces and cellars. These places can be found in many building types including barns, historic buildings, churches and even modern houses.

Demolition, renovation works, changes in use, the move towards air-tight buildings and artificial lighting, all pose a threat to bat populations.

The most obvious sign is their mouse like droppings which are brown or black, around 4 to 8mm long and crumble easily, although even these can sometimes be hard to find. Other signs include insect remains such as butterfly wings, grease marks on rafters or around holes and cobweb free corners.

Due to the decline in bat numbers, all UK species of bat are protected under British law within the Conservation of Habitats and Species Regulations 2017 (as amended) and the Wildlife and Countryside Act 1981 (as amended).

This makes it illegal to:

• intentionally or recklessly kill, injure or capture bats;
• deliberately or recklessly disturb bats (whether in a roost or not); and
• damage, destroy or obstruct access to bat roosts

If a development, which requires planning permission, has the potential to impact bats or their roosts then a Bat Survey Report should be submitted as part of the planning application. Any survey work should be undertaken in accordance with Natural England standing advice and the Bat Conservation Trust’s (BCT) Good Practice Guidelines. If bats are present then a European Protected Species (EPS) licence will be required to legally undertake the works.

If the proposed works do not require planning permission such as roof repairs, pest control or timber treatment, you should contact the Bat Conservation Trust Helpline on 0345 1300 228 (www.bats.org.uk) before works start and follow their advice on how to proceed. If bats are found then works must stop and BCT and/or Natural England must be contacted.

In line with Natural England and Bat Conservation Trust guidance Breathable Roofing Membranes (BRMs) or Non-Bitumen Coated Roofing Membranes (NBCRMs) should not be installed into a roof used by bats. This is because there is considerable evidence that the spun-bond filaments in modern membranes pose a serious threat to bats as a result of entanglement.

Currently the only ‘bat safe’ roofing membrane is bitumen 1F felt which does not contain polypropylene filaments but is hessian reinforced.

Bats are nocturnal and most species find artificial lighting very disturbing. Lighting should be avoided on sites where there are bats roosting or habitats such as mature trees, hedgerows and woodlands which are likely to be important for foraging and commuting bats.

Guidance note 08/18 produced by the Bat Conservation Trust and Institute of Lighting Professionals:

• Direct any task lighting away from important habitats or roosts
• Set any external security lighting on motion-sensors and short (1min) timers.
• All luminaires should lack UV elements. Metal halide, fluorescent sources should not be used.
• Use LED luminaires where possible due to their sharp cut-off, lower intensity, good colour rendition and dimming capability.
• Adopt a warm white spectrum (ideally <2700Kelvin) to reduce blue light component.
• Luminaires should feature peak wavelengths higher than 550nm to avoid the component of light that is most disturbing to bats.
• Only use luminaires with an upward light ratio of 0% and with good optical control.
• Mount luminaires horizontally, i.e. no upward tilt.
• Internal luminaires can be recessed where installed in proximity to windows to reduce glare and light spill.

As a last resort, accessories such as baffles, hoods or louvres can be used to reduce light spill and direct it only to where it is needed.

All breeding birds are protected under the Wildlife and Countryside Act 1981 (as amended) making it a criminal offence to take, damage or destroy the nest of any wild bird while that nest is in use or being built.

Some bird species such as Barn Owl and Peregrine (listed in Schedule 1) are afforded even greater protection. It is an offence to intentionally or recklessly disturb these birds or their young at, on or near an ‘active’ nest.

The onus is on you to ascertain whether birds may be nesting or using your trees, hedgerows or buildings, to ensure you do not contravene this legislation. This may, for example, require delaying hedgerow cutting, vegetation clearance or building works until after the bird nesting season.  The nesting season for birds can be considered to be from March to August, although some birds do nest outside of this period. 

Historic England have published guidance on regularly sweeping chimneys and fitting guards to stop nesting birds because blocked chimneys are considered to be a significant cause of thatch fires.

Guards should be fitted and sweeping should be done outside of the bird nesting season from September to February. If this needs to be done within the bird nesting season then checks must be made to ensure there are no nests in use or being built, in accordance with the Wildlife and countryside act 1981 (as amended).

March 2019 saw widespread public concern over the practice of netting trees and hedgerows to prevent the establishment of bird nests. Netting should only ever be used as a last resort, if absolutely necessary, and all reasonable precautions must be taken to ensure that no wildlife becomes trapped in the netting. Any netting must be properly maintained and checked regularly to ensure it is both safe and effective.

Whilst some birds can be considered a pest or nuisance when using buildings, it is important to remember that many species are declining and it is crucial that we support our wildlife by providing a place for nature and biodiversity within our urban areas.

If bird prevention measures are absolutely necessary then the following alternatives to netting should be investigated and used where appropriate:

• Flying of predatory birds – in Winchester we have a Peregrine pair which provide a natural solution.
• Heavy duty mesh or spikes as opposed to netting - checks should be made by a qualified ecologist to ensure bats are not impacted by the instalment of these features. Any prevention measures should be installed outside of the bird nesting season.
• Audible scarers and optical gels can also be used but these too have the potential to affect bats and other protected species so a qualified ecologist should always be consulted prior to installation.