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Credit - Srburke, CC BY-SA 4.0, via Wikimedia Commons.
Credit - Srburke, CC BY-SA 4.0, via Wikimedia Commons.

When Wildlife Meets Heritage! The Importance of Factoring Bat Surveys into Project Planning

3 March 2024

Today, as we mark the annual celebration of World Wildlife Day, the Architectural Heritage Fund (AHF) is looking at bat surveys and reflecting on why they are an important part of the planning process for many historic building regeneration projects across the UK.

There are 18 different species of bats in the UK and all of them and their resting places (roosts) are legally protected. This means that by inadvertently or deliberately disturbing bats or interfering with their roosts, you could be breaking the law. Some of the activities that can affect bats include renovating or converting a building, repairing or replacing a roof, and repointing brickwork. As a result, it is necessary to carry out a bat survey when there is a likelihood that bat roosts are present in a building. However, the presence of bats does not mean that development work cannot take place. In fact, the survey will also assess effective methods of mitigating bat disturbance, enabling the project to continue without causing harm to them or their roosts.

It’s also worth noting that there are already several different established ways to ensure that bats are maintained and protected, while also reducing their impact on the fabric of historic buildings and the people who use them. Bats in Churches, for instance, is a unique project that brought together partners from across the heritage and conservation sectors to discover different ways to help churches and other historic buildings to live happily alongside their bats, allowing them both to thrive. You can find more information, resources and case studies on this topic on the Bats in Churches website.

So, what exactly does a bat survey entail?

While a bat survey can help you to determine whether or not bats are present in a building, they can also establish more specific details, such as the species and estimated number of bats present, access points, and how and when bats are using the building.

There are two phases of a bat survey. The initial phase is undertaken in the daytime and is often referred to as a Preliminary Roost Assessment. Its purpose is to identify and catalogue evidence of bats and bat activity. During the assessment, a licensed bat ecologist will be looking for signs that bats have been or are using the building; features in the building that could potentially provide a roosting place; and the surrounding area’s suitability for bats. If they conclude that there is no potential for bats to be affected by the development proposal, then no further surveys are likely to be required.

If bats are found during the first phase, or survey work was inconclusive, then a second phase is required. This phase, undertaken at dusk or dawn, is often referred to as a Bat Emergence and Re-Entry Survey, and is designed to see if any bats emerge or re-enter a structure, as well as determine bat species, population numbers and entry and exit points. During the survey, the licensed bat ecologist(s) standing outside of the building will use hi-tech equipment like bat detectors and infrared or thermal imaging cameras to monitor bat activity. This phase often requires two or three survey visits, and each one must be at least three weeks apart.

Why is it important to factor bat surveys into your project planning?

While a Preliminary Roost Assessment can be carried out at any time of the year, Bat Emergence and Re-Entry Surveys must be undertaken when bats are active, which is usually between May and September. Demand for licensed bat ecologists is very high during this period, and weather can also play an important factor, as high winds and heavy rain may result in the survey having to be postponed. Additionally, bat surveys are commonly needed as part of an application for planning permission. If you avoid this requirement and bats are discovered when works have started, it could cause delays to your work. It is best to factor bat surveys into your project planning from an early stage, as this will allow for bats and any mitigation efforts that may be needed to be accounted for in the project design, schedule and budget.

If you are looking to commission a bat survey for your project, the good news is that this is an eligible cost that an AHF grant can cover. For example, the AHF recently awarded a Project Viability Grant to Birse Community Trust towards a bat survey, report and bat mitigation plan for its Ballogie Soutar’s Shop project

Find out more about the support we provide in:




Northern Ireland 


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