Wolvercote Railway Tunnel

Wolvercote Railway Tunnel Geoff Billington Greena Ecological Consultancy • Wolvercote railway tunnel is 133m long carrying the local Chilterns Oxf...
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Wolvercote Railway Tunnel

Geoff Billington

Greena Ecological Consultancy

• Wolvercote railway tunnel is 133m long carrying the local Chilterns Oxford to Banbury rail line • The tunnel contains a single track set slightly off centre • In the past it contained two tracks set at a lower level • It is formed with a roof lining of brick over stone abutments • There are a couple of cracks and five deep drain holes in the roof and holes in the walls where mortar is missing

The tunnel lies beneath the very busy and highly illuminated Oxford northern ring road




 The line is used by local passenger trains and a small number of freight trains, restricted to a maximum speed around 30mph up to a couple of dozen trains use the line through the tunnel in a 24hr period  Few or no trains run between 2200 and 0500  The proposal is to upgrade the line back to a twin track with increased frequency and speed, with maximum of up to 80 trains per day, around a dozen trains passing between 2130 & 0630 only a couple of freight trains passing between 0030 & 0530  Passenger trains to be able to travel up to 70 mph, freight trains continue restricted to 30 mph  The scheme has been the subject of a public inquiry November 2010 to January 2011 the Inquiry was reopened in May 2012 mainly because of concerns over the potential effects to bats  Approval for the scheme was given in October 2012

Initial surveys A series of surveys were undertaken by between July 2009 and May 2010 to inform an Environmental Statement  7 dusk emergence surveys  1 dawn re-entry survey  Full night of monitoring in autumn  3 night roost counts  4 separate nights of Anabat monitoring  17 continuous nights of Anabat monitoring in spring  3 hibernation surveys  Single night of autumn trapping

2009/ 2010 findings  Maximum of 13 myotis bats day roosting in the tunnel during September, none in April & May  Two Natterer’s hibernating  Daubenton’s, Natterer’s, Common & Soprano pipistrelle bats day roosting  Brown long-eared night roost  A low level of swarming possibly occurring in early September  The tunnel provides an important corridor for Daubenton’s, Natterer’s, Pipistrelle and Long-eared bats  Noctule and Leislers bats feed in the northern cutting

Initial 2010 proposed solution/ mitigation  Exclude bats from roosting in the tunnel  Use lighting to prevent bats from using the tunnel  Create a small scale replacement tunnel into the embankment to function as a year round roost and possibly a swarming site as well

2010 proposal for hibernacula within embankment

Taken from the Environmental Statement

Taken from the Environmental Statement

Summer 2010 onwards

A series of surveys undertaken by Greena 2010 - 2012  Annually 2 dusk emergence surveys in September Bat box inspection in September Up to 8 weeks Anabat or Batcorder static bat detector monitoring between August & October Hibernation survey  2010 3 nights of autumn trapping survey in 2010  2011 42 nights of lighting trial study in August & September including 9 nights of observations & 7 emergence surveys  2012 April 2012 Batcorder static bat detector monitoring for 4 weeks 2 radio tracking studies in May & September Off site transect and static bat detector monitoring Casualty survey

2010 late summer/ autumn swarming survey • Three

sessions were carried out during August & September 2010 • Surveyors set up mist nets and harp traps across both entrances to catch bats after the trains had finished for the night • Two harp traps were set up side by side at one entrance with shielding netting attached to either side and beneath traps to divert bats into them • Two levels of mist nets were set up across the other entrance • Surveyors stationed themselves close to the mist nets and remained there for most of the remainder of the night leaving by 0500

2010 autumn swarming survey captures

10 9 8 7 6 27/08/2010 5




3 2 13/09/2010



0 Daubenton's Natterer's

27/08/2010 Pipistrelle Long-eared

Emergence surveys • Two emergence counts have been carried out each September as peak bat numbers have been found to occur at this time of year • Surveyors stationed themselves at each tunnel entrance equipped with radio sets so overall movements of bats in or out of either entrance could be determined • The emergence surveys were conducted when trains were still operating

Maximum monthly emergence counts 14

12 10 8 Myotis


Pipistrelle Long-eared

4 2 0 Long-eared Pipistrelle Myotis

Hibernation 2.5


1.5 Natterer's Daubenton's 1


0 Jan-10



Static bat detector monitoring • Initially in 2009 & 2010 monitoring was just carried out at one of the entrances this was extended to both entrances and the middle of the tunnel in 2011 • Over the first three years Anabat detectors were used • In 2012 the system has been changed to Batcorders as they provide much higher quality results, are calibrated to all be of the same sensitivity and have bespoke auto ID software that facilitates relatively easy handling of thousands of files and produces consistent analysis • To compare Anabat and Batcorder results a conversion factor based on comparison research by Adams, Jantzen, Hamilton & Fenton published in 2012 has been used

Batcorders in 2012 • Box units were used that contain their own waterproof microphone, the Batcorder, a control unit and 10A lead acid battery they will operate for around 5 weeks • Daily after the end of recording sequence the control unit transmits: battery voltage, SDHC card space, number of files recorded the previous night and a test tone transmission to check the microphone performance

• Monitoring is carried out for two months August - October and will carry on until 2017

Anabat recordings 2010 & 2011

Bat boxes  A variety of 20 Schwegler bat boxes were installed in early 2011 on trees in the cuttings either side of the tunnel as alternative roosting sites

 Inspection in September 2011 showed two being used by individual Pipistrelle bats, a male Soprano pipistrelle was present in one  September 2012 found the male bat with a harem of 6 females in one of boxes  Monitoring will carry on until 2017

2011 lighting trial research study At the request of Natural England a full scale trial of a lighting system outlined in a draft EPS licence application was conducted in August, September & October 2011 • A computer controlled system was installed to control light sequences • Lighting commences in the middle of the tunnel and then within half a minute spreading out to both entrances

Lighting system design

Lighting trial o The design brief was to work with minimum level of lighting to avoid dazzle

risk to train drivers. o First set of lights produced around 40 lux, the effects on bats started to decrease markedly within a week, suggesting a number of them were rapidly getting aclimatised to the lighting levels o Lights were changed and the level increased to around 80 lux, this had a pronounced and sustained effect of positive displacement to safety of around 2/3 of the bats. o The sequence of lighting was designed to replicate the maximum possible number and length of trains in any night expected to occur in the future o Four surveyors stationed themselves at entrances and in the tunnel and recorded over a continuous period of up to 6hrs with up to 43 sequences o 8 min total sequence: 1 minute observation before lights start, 2min illumination, 2 minutes until after lights off, then 3 minute break before starting again, bats scored negative if staying in flight in the tunnel and positive if they headed rapidly out or went to roost


Lighting trial conclusions  Bats are

not disturbed from night roosting in crevices some actively seek to enter into crevices when the lights come on particularly looking for places in less illuminated places such as immediately above the light units  Over 60% of bats were displaced to safety by the 80 lux lighting  The effects on the bats are very short term within seconds the majority of bats that had exited from the tunnel re-entered  Higher light levels will increase the percentage of positive displacement  To ensure bats have sufficient night roost sites boards/ tiles will be fastened to walls above each of the lighting units to provide night roosting sites

2012 baseline survey year Hibernation Winter inspection Radio tracking Two sessions of trapping, tagging and ringing bats tracking 18 bats in May and 23 in September for two week periods, including use of unmanned radio tag loggers to record when tagged bats visit the tunnel area Bat detector survey transects Three 7km long transects of the wider area along rivers and the canal with 1 week static monitoring both carried out in August and repeated in September

2012 Casualty surveys Carried out whilst attending for other surveys or equipment maintenance on 21 nights Static bat detector monitoring surveys 12 weeks: 4 in April, 8 between August & October Bat boxes Inspection in September Emergence surveys Two surveys in September Casualty scavenger survey Using 10 wildlife video cameras running for a month

14 bat species recorded using the railway corridor 2009 - 2012 • Common Pipistrelle (Pipistrellus pipistrellus)

• Soprano Pipistrelle (Pipistrellus pygmaeus) • Nathusius Pipistrelle (Pipistrellus nathusii) • Noctule (Nyctalus noctula) • Natterer’s (Myotis nattereri) • Daubenton’s (Myotis daubentonii) • Alcathoe (Myotis alcathoe) • Brandt’s (Myotis brandtii) • Whiskered (Myotis mystacinus) • Bechstein’s (Myotis bechsteinii) • Long Eared (Plecotus spp.) • Barbastelle (Barbastella barbastellus) • Leislers (Nyctalus leisleri) • Lesser Horseshoe (Rhinolophus hipposideros)

Conclusions  Surveys to date have revealed the importance of the railway corridor and

tunnel as a bat flight route of at least 14 bat species  The original proposal to lose the tunnel roosts and corridor and has been abandoned  The current proposal is to retain the flight corridor through the tunnel, retain and enhance roosting sites in the tunnel and provide a lighting system that triggers when a train is coming to alert and move bats out of the way of trains  Bats do not breed in the tunnel and only individuals hibernate in winter  Myotis swarming does not appear to occur here  Small numbers of Common & Soprano pipistrelle bats occasionally roost in the tunnel and individual males use it as a lekking site in autumn  Individuals/ small numbers of Brown long-eared bats roost in the tunnel in August/ September 2011 swarming activity took place, none was recorded in 2012  Monitoring will be carried out until 2017

Acknowledgements • Chilterns Railway for funding the surveys and research through ERM • Atkins for providing safety, maintenance & COSS staff • ERM the overall ecologists

• Natural England for licensing activities • The residents in Oxford area for tolerating our night activities

Greena courses & workshops We run specialist training courses & survey workshops that have included to France & Crete

Bat in Woodlands held in West Somerset has been running since 2002 a comprehensive view on surveying woodlands with workshops on the techniques including trapping and visits to tree roosts in Horner Woods where Barbastelle’s roost.

Advanced bat survey techniques

held at Stourhead Estate in Wilts running for last couple of years, a really good place with lakes for bats in 2011 53 bats of 12 species were caught, 11 species on the first night, course includes trapping and radio tracking.

European bat workshops 3 years in France and the last two in Crete, running for the last 5 years, week long trips staying in comfortable Gites, Hotels or Apartments. Trapping and bat detector surveys in collaboration with local biologists. Our last trip to Crete in May 2012 we caught nearly 800 bats over the week. On these workshops we encounter a mixture of bats some we see in the UK and other species particularly in Crete are unique to the eastern Mediterranean, extensive handling opportunities.

Intensive training we have supplied small groups or individuals with specialist technique training including for handling, trapping and radio tracking. If you are interested in details email me: [email protected] or see our web site: greenaeco.co.uk or give me a ring 077487 42475

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