Introduction
- Project description
- In 2009, a noctule Nyctalus noctula maternity roost (≤75 bats) was recorded in a tree, accidentally felled in 2011 over public safety concern. Rapid response mitigation returned a noctule maternity colony in 2012 and 2013. This case study exemplifies the need for sharing ecological data within organisations and third parties.
- Ecologist’s name and contact details
- Name: Chris Damant. Company: Bernwood ECS Ltd. Address: Hensmans Farmhouse, Nearton End, Swanbourne, MK17 0SL. Email: chris@bernwood.net. Mobile: 07817131683.
- Site postcode
- MK5 6FQ
- Planning authority
- Milton Keynes Council
- Brief site description
- The noctule maternity roost was found inside an ash Fraxinus excelsior tree with a central rot hole. Woodpecker holes allowed bat access into the central rot hole. The tree was situated on the edge of a ride on the north side of ancient semi-natural woodland. The ancient semi-natural woodland is approximately 25 ha in area, with approximately 6 ha of buffer around it. It has a canopy mainly composed of ash and oak and an understory of hazel. It is located in south western Milton Keynes, and the woodland cover in this area was recorded in the Domesday Book of 1086.
Pre-works roost structure
- Type of structure
- Other
- Use
- Other
- Approx. age
- <100 years
- Main construction material of walls
- Other
- Roof design
- No Roof Applicable (Tunnel or Bridge)
- Roof material
- Not Applicable
- Internal roof structure
- Not Applicable
- Lighting present on site and its proximity to the roost
- No lighting on site.
- Photos or annotated figures of roost structure
Pre-works roost description
- Species
- Noctule
- Number of bats max count
- 75
- Type of roost
- Maternity Roost
- Evidence of bats
- Bats Recorded Emerging/Re-entering
- Roost location
- Other
- Aspect of roost
- Various
- Height of roost entrance (m)
- Various; 2-3 m.
- Roost material(s)
-
- Other
- Nearest commuting feature
- Woodland
- Distance to nearest commuting feature (m)
- 0 m; woodland ride adjacent.
- Photos or annotated figures of roost
Proposed works
- Description of works
- Contract staff operating on behalf of the landowner were employed to conduct routine ride side and tree safety management work. The contractors determined the ash tree to be a public safety concern due to characteristics of internal rot and inclination over the main woodland ride. Two grey squirrel emergences from the tree led to the contractor’s assessment that the tree was not suitable as a bat roost, and the tree was felled. Upon learning what occurred, the landowner halted the processing of the timber and contacted Bernwood ECS Ltd. for designing and implementing bat mitigation and compensation schemes. Within hours of the felling, the roost was confirmed vacant, Natural England was informed of the events, and a rapid-response mitigation strategy with training programme agreed.
- Type of impact upon the roost
- Long-Term Roost Modification and Roost Loss
Proposed mitigations
- Type of mitigation
- Mitigation
- Specific technical detail of measure
- Survey information from 2009 and 2011 along with photographs and night-shot video footage were used to identify bat access points including their heights and orientations. The mitigation involved reinstating the trunk against the nearest suitable tree, also ash. A high lift was used to assist with the lifting of the felled trunk, fastening it to the live ash tree using 19mm steel banding. Protective rubber straps were placed between the steel banding and both tree trunks to reduce the impact on the live tree. The access points were orientated to recreate their original positions prior to felling. A replacement top was constructed from ash wood to shelter the roost, to replicate internal environmental conditions, and to prevent an increase in decay through weathering. The top was similarly bonded to the trunk with steel straps. The reinstated section plus top totalled 3.4m tall by 0.5m wide (1.1m wide when attached to the live tree). The works took place over five consecutive days after the tree’s felling.
Other compensation measures were implemented, such as five Schwegler woodcrete 2FN bat boxes and cavities carved into nearby ash trees to stimulate rot (the crown weight reduced to maximise tree longevity). No post-development monitoring of these measures was not conducted by Bernwood ECS Ltd.
- Relevant annotated figures
- Roost location
- Other
- Aspect of roost
- N
- Height of roost entrance (m)
- Various; 2-3 m.
- Roost material(s)
-
- Other
- Nearest commuting feature
- Woodland
- Distance to nearest commuting feature (m)
- 0 m; woodland ride adjacent.
- Photos or annotated figures of roost
Monitoring data
- Length of monitoring proposed
- 2 years post-development.
- Frequency of monitoring
- Annually.
- Type of monitoring
- Dusk and Dawn Survey
- Date and time
- 8th July 2012 22:00
- Evidence recorded
- 37 noctules recorded emerging in 2012. Video evidence on YouTube: 1) https://youtu.be/J-t6Rmehscg and 2) https://youtu.be/vhGKF24UmpQ
- Interventions made
- None.
- Type of monitoring
- Dusk and Dawn Survey
- Date and time
- 27th May 2013 22:00
- Evidence recorded
- 46 noctules recorded emerging in 2013. Video evidence on YouTube: https://youtu.be/0dg_0kVNJQ4
- Interventions made
- None.
Final details
- Lessons learned
- This case study highlights the advantage of resourceful, time-sensitive responses to accidental damage of ecologically important sites. The rapid response of the landowner improved the prospect of delivering a creative conservation strategy with positive results. The landowner also reduced the likelihood of future incidents through addressing weaknesses in operational structure, specifically through communication channels within the organisation itself and with third parties conducting works. This case study also underscores the value of biological recording and photographic evidence, as it significantly improved the effective delivery of mitigation by ensuring correct bat access point heights and orientations.
This work has since been published in Conservation Evidence to inform practitioners on tree roost displacement:
Damant C. & Dickins E. Rapid response mitigation to noctule Nyctalus noctula roost damage, Buckinghamshire, UK. Conservation Evidence (2013) 10, 93-94.
The landowner has continued informal monitoring of all implemented measures since 2013. A 2020 update is included:
• The tree roost mitigation structure was used by roosting noctules (and possibly breeding) quite a bit and Paul Moon and myself monitored it informally. We last had bats in there, for certain, in June 2017.
• Noctules have never been found any of the bat boxes provided.
• we now know of six trees, all ash, which are used as roosts from time to time. but there are three ash trees in the northern section with woodpecker holes, which now seems to be the main concentration.
• One of the trees used by noctules is situated about 10 metres behind the original roost tree but it is not possible to confirm this was one of the trees that were cut to create artificial cavities in the area of the roost.
'the mitigation was shown to work in the short term and allowed the noctule colony time to adapt to more favourable alternative roosts in trees with woodpecker holes within the woodland.'
M. Kincaid. The Parks Trust. Pers. comm. 2020
