Environmental Statement volume 4 - Chiltern Evergreen3

Chiltern Line September 2009Bat Dusk and Dawn Surveyspecies. Surveyors were in positio n 1 ½ hours before dawn and continued for up to ¼ hourafter dawn for the dawn surveys.2.4 All surveyors were eq uipped with a Stag Elec tronics Duet bat d etector u sed in combine dfrequency division and heterodyne mode. Registrations were recorded on MP3 recorders andnotes were made on species, behaviour, time of registration, location and di rection of fligh twhere possible, including incidental observations from surrounding habitats. Where it was notpossible to i dentify a bat spe cies o n site, audi o recordings were late r a nalysed usingBatSound St andard Soun d Analy sis S oftware (V ersion: 3.31, 2 001, Pettersson ElektronikAB).2.5 A singl e mi st netting survey wa s al so undertaken at Wolvercote Tunn el on the 11/1 2th o fOctober to a llow dete ction of swa rming bats and identification of these sp ecies thro ughcapture. Mist netting i s suitable fo r scientific studie s whe re identification of Myotis ba ts tospecies level is required (BCT, 2007). The mist netting survey was undertaken by 2 licensedbat workers (Natural England 20083493 & 20093275 all species all counties) and an assistingecologist under a project specific survey licence (20092793). A static mist net, approximately9 metres in length, comprised of fine nylon netting with loose pockets held in tension between2 pole s, was po sitioned over th e u pper mo st section of th e no rthern t unnel entranceapproximately 6 metre s above ground level and lo wered each time a bat was caught for i tsremoval (Mitchell -Jones, 2004 ). The mist net was po sitioned at 23:00 and the surv eycontinued until 03:30 the followin g morning (whe n possession of the rail line was availa ble).The additional survey at Wolvercote tunnel was undertaken in sub-optimal conditions of below10°C.2.6 Immediately prior to the mist netting survey the length of th e Tunnel was in spected for si gnsof roosting bats. This included a check of all pot ential roosting cavities for the pre sence ofbats or evidence of roosts i.e. staining or droppings, and an inspection of the Tunnel floor forfurther evide nce of roosts i.e. droppings, which could in dicate the prese nce of fu rtherunobserved cavities.2.7 In addition, a t Wolvercote Tunnel on the 28 th September and 11 th and 17 th October a staticmanual detector (AnaBat SD1 Compact Flash Bat Detector) was set in pl ace at the n orthernentrance of the Tunnel, with 1 also being placed at the southern entrance of the Tunnel on the11 th October. The se remained in place throughout the course of the survey. The d etectorworks in fre quency divisi on mo de with zero -crossings an alysis and only records whenecholocation calls activate the unit (Titley Electronics, 2008). Recordings were later analysedusing AnalookW version 3.3q (Corben, c. 2006).2.8 All surveys were u ndertaken by an exp erienced licensed bat worker holding an all co unties,all species licence (Licence Number 20083493) with additional ecologists assisting with thesurveys.Site Status Assessment2.9 The surveyed structures/trees have been evaluated to a ssess which of the followi ngcategories they fall into, if any (Mitchell-Jones, 2004):maternity site, where young are born and raised to independenceKeystone Environmental 6