Bat survey and mitigation at Historic Buildings in Doncaster under the National Scape AMS and DS Framework

Background

BSG Ecology was commissioned to provide ecological services at Mansion House and Cusworth Hall, during 2014 and 2015, as a Tier II supply chain partner under the National Scape Asset Management, Surveying and Design Services (AMSandDS) framework, for Faithful+Gould. Our role in both these projects was to establish and advise on how to alleviate the risk of an impact on bats during building maintenance and fabric repair work at these two historic properties, belonging to Doncaster Metropolitan Borough Council (DMBC).

Mansion House is a Grade 1 listed civic building located in Doncaster City Centre dating from 1748. Mansion House, together with neighbouring No’s 1-3 Priory Place (also part of the planned works) include a Ballroom, Mayoral Bedroom, Council Chamber, Drawing Room and Great Kitchen, as well as Doncaster Tourist Information and office space. Together, these buildings form a complex arrangement of interconnecting pitched and hipped roofs varying between one and four storeys in height. Proposed works included re-covering several major pitched/hipped roofs, repairs to chimney stacks and other roofs and replacement of roof lanterns.

Cusworth Hall is a Grade I listed Palladian style Country House, dating from the 1740’s and set within historic parkland, approximately 3km northwest of the centre of Doncaster. The hall comprises a central, three-storey Main House with two-storey East and West Wings set either side of the north façade and later additions of a Chapel, Library and Edwardian Wing. Proposed works included re-covering parts of the triple pitched main slate roof, the pitched stone-tile roof of the west wing and hipped clay-tile roof of the Edwardian Wing.

Mansion House Doncaster Bat SurveyMansion House

Working closely with Faithful+Gould and DMBC, BSG Ecology was able to establish a safe means of access to all roof voids within the Mansion House complex as well as full access to rooftop walkways. Access at rooftop level was particularly important as it enabled a close-up and detailed inspection of roof coverings, chimneys, flashings and parapets; the majority of which were not visible from ground level due to the complexity of the buildings being surveyed and their juxtaposition with other buildings in this town centre location.

One of BSG Ecology’s experienced bat ecologists studied building plans to ascertain how to gain access to roof voids, and subsequently inspected each roof void for evidence of bats and to establish whether there were any potential bat roost access points. No evidence of bats was found.

BSG Ecology reviewed the distribution of historic bat records for the urban area of Doncaster (supplied by South Yorkshire Bat Group) and studied the surrounding habitat using internet based aerial photographs and maps for context as part of the work.

Mansion House is located in an area of high density commercial development in Doncaster City Centre. The area immediately surrounding the site comprises buildings and hard standing with no vegetation cover within 300m and only small patches of green space in the form of the yards of terraced houses 300-500m away. It was considered this would likely limit bat foraging opportunities and the potential for roosts either at Mansion House or close by. The nearest area of potentially favourable bat foraging habitat is the Sheffield and South Yorkshire Navigation Canal 500m to the north. The nearest significant areas of green space (a playing field and a cemetery) are located more than 750m to the south and east. There is no habitat connectivity between the site and potential bat foraging habitat in the wider area.

There were found to be no records of bat roosts within Doncaster City Centre. The two nearest records related to individual common pipistrelle bats taken into care (injured) from an area of terraced housing approximately 300m to the east. The only other record of a bat within the City Centre (500m), related to an injured Daubenton’s bat Myotis daubentonii found by the Sheffield and South Yorkshire Navigation Canal.

Historic buildings can offer diverse roosting opportunities for a variety of bat species and it does not always follow that a negative daytime survey result means there are no bat roosts present. In some cases, further survey work may be required in order to add confidence. In this instance, based on the daytime survey and desk based review, BSG concluded that the lack of bat foraging opportunities in the local area and poor habitat connectivity significantly reduced the probability of a bat roost being present. As a result, it was considered that further survey work, such as bat emergence surveys, was not necessary to support the negative preliminary assessment.

A thorough and rational approach by BSG ecologists, with significant experience in bat ecology and a detailed knowledge of how bats utilise buildings and landscapes, gave DMBC confidence in a negative result that was clearly reported and undertaken with reference to current Bat Conservation Trust Good Practice Guidelines (Hundt, L. 2012).

Cusworth HallRoof work at Cusworth Hall

BSG Ecology undertook a daytime bat survey of all areas of Cusworth Hall and subsequently carried out dusk emergence and dawn re-entry surveys. The only evidence of bats found during this survey work were three old and decaying brown long-eared bat Plecotus auritus droppings in the West Wing. No roosts could be identified. However, desk study data, the presence of numerous features with bat potential and observations of bats foraging during the dusk/dawn surveys led BSG Ecology to conclude that there was a risk of encountering bats or roosts during the proposed works.

South Yorkshire Bat Group provided a significant number of records of bats relating to Cusworth Hall and Park including historic records of brown long-eared bat droppings in the loft voids of the Main House, East Wing and Clock Tower and a record of three pipistrelle bats Pipistrellus sp. roosting behind window shutters of the gatehouse.

BSG Ecology recorded common pipistrelle Pipistrellus pipistrellus, soprano pipistrelle Pipistrellus pygmaeus, noctule Nyctalus noctule, Daubenton’s bat Myotis daubentonii and brown long-eared bat in Cusworth Park during the dusk/dawn surveys. The Parkland surrounding Cusworth Hall, which includes broadleaved woodland and a large lake, is considered likely to provide good quality foraging habitat for a number of bat species. Mature and veteran trees in the Park may also provide bat roosting opportunities and there are a number of bat boxes on trees.

Whilst there was a potential risk of encountering bats or bat roosts during the proposed works, without any current evidence of roosts, there were no grounds for making a European Protected Species (EPS) Licence application to Natural England to derogate from the legal protection afforded to bats. It was therefore agreed that a precautionary method of working would be put in place and an experienced bat ecologist was present on site when works commenced on the West Wing roof.

Reasonable avoidance measures included work being undertaken at a time of year (winter) when it was considered bats were least likely to be present in roosts under roof tiles i.e. avoiding disturbance to bats. In addition, the roof covering was replaced like-for-like with all bat roost access points being re-instated so that bats could return to the same access points the following season.

As work began, many bat droppings were found in crevices under the large stone tiles that were not possible to see in advance without removing the tiles.

As evidence of use of the roof by bats was discovered, work stopped. The experience and knowledge of the client team including BSG Ecology and Faithful+Gould enabled prompt liaison with Natural England specialist Wildlife Advisors and the Local Authority Ecologist. This led to a rapid solution which avoided harm to bats. The necessary amendments to the roof design and method of working were agreed, and works were able to continue within 24 hours.

Outcome

On both of these projects, a focussed and considered assessment on the status of bats within large and complex historic buildings was required. Working with the client team and local authority, BSG Ecology delivered a practical timely solution that avoided harm to bats whilst enabling work to proceed. At Cusworth Hall, in particular, we avoided a lengthy and potentially costly delay of 2-3 months for the client.

Bat survey and mitigation at Historic Buildings in Doncaster under the National AMSandDS Framework – Project Profile

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