The following information is an update of the article Bats on Fair Isle in 2015 and a historical overview of bat records by Andrew Chick and David Parnaby published in the 2015 Annual Report.
During 16th-21st October 2015, a single Anabat Express (a passive bat recorder that records any sounds detected within the range of bat calls) was left recording between dusk and dawn on Fair Isle by Andrew Chick, a visitor to the Obs. It was located at the Obs every night except 19th, when it was placed at Chalet. Although bats are known from Fair Isle only as rare vagrants, their largely nocturnal behaviour means that they may be under-recorded. Remarkably, this speculative effort resulted in three bat calls being recorded on the night of 17th October, two from a Nathusius' Pipistrelle Pipistrellus nathusii and a single Common Pipistrelle P.pipistrellus, the latter being the first confirmed record from Fair Isle. There were no other bat calls recorded during the period (nor were any recorded during two nights' effort in Lerwick on 15th and 22nd October).
Data collected from the static Anabat Express was analysed with the aid of Anabat software and produced the following results:
The call range frequency for this species is 35.5 - 41.9 kHz (Russ, 2012). Two calls were recorded within this frequency, at 18:52hrs and 21:17hrs.
Both of these calls are presumed to relate to the same individual, given the rarity of bat records on Fair Isle. This species was confirmed as resident in the UK as recently as 1997 (Bat Conservation Trust) but is also a strongly migrant species. Although specific identification is difficult unless it is caught or its call is recorded, it is thought to be the species that occurs most frequently in Shetland (www.nature-shetland.co.uk).
The call range for this species is 43.3 - 49.9 kHz (Russ, 2012) and a call within this frequency was recorded at 19:59hrs.
This remarkable record represents the first proven occurrence of this species on Fair Isle and Shetland. Although it is possible that some of the earlier unspecified pipistrelles may have been this species, it is notable that all those examined in the hand have proved to be Nathusius' Pipistrelle.
To put the night of 17th October 2015 into context, all other bat records from Fair Isle are collated below [and updated for 2016-18]:
17th October 2015 • one (see above).
3rd May 1989 • flown to Aberdeen and released
26th October 2011 • found exhausted at Barkland during strong easterly winds and rain, later released on Fair Isle after a short period of recuperation.
17th October 2015 • one (see above).
26th May 2016 • one found freshly dead near the Double Dyke
29th May 2016 • another found moribund at Meadow Burn. Although it appeared to perk up after being taken into care, it was later found dead where it had been released. It weighed just 6.1 g, substantially less than the average weight of around 10 g.
27th September 1973 • found roosting in a wall at Skerryholm but later died
3rd June 2006 • seen in South Ramnigeo in flight, considered 'almost certainly Pipistrellus sp'
31st May 2009 • one seen in flight at Chalet, considered to be probably a pipistrelle sp.
19th October 2016 • a presumed pipistrelle species was seen in South Harbour and at the Haa.
23rd May 1968
22nd August 1996 • a 'small bat' seen in flight at Field
13th October 2004 • one seen in flight at the Chapel
11th June 2011 • one in flight over the Vaadal, described as 'rather pale and larger than a pipistrelle'
26th September 2016 • one over the Obs was considered to be probably larger than a pipistrelle
20th October 2017 • an unidentified bat was observed flying into the Kirn 'o Skroo
It is possible that some earlier records were not documented, but it is clear that bats have always been very rare visitors to Fair Isle, although the 2015 records hint at further discoveries to be made.
A detailed review of all Shetland bat records up to the end of 2013 by Paul Harvey can be found on the Bat Conservation Trust website.
Many thanks to Nick Riddiford and Paul Harvey for help in collation of the Fair Isle bat records and to Micky Maher for commenting on the identification of the Common Pipistrelle.
Russ, J. 2012. British Bat Calls: A Guide to Species Identification. Pelagic Publishing.
It should be noted that all bats are protected and should not be handled (unless to tend to an injured individual), but as potential carriers of rabies, anyone lucky enough to find a bat on Fair Isle should content themselves with getting pictures and not handling it.