There was a tiny Pipistrelle flying around the streetlights and into the sycamores this evening when I came back from Portnahaven. They are only fairly common here in Port Charlotte. We put a bat box up in the lodgepole pines in the garden two or three years ago to see if we could attract them, but there has never been any of the tell-tale droppings that would let us know that they are taking advantage of our hospitality.
There are two species of Pipistrelle, both of which I understand occur on Islay, the Common Pip and the Soprano Pip, which are distiguished through the frequencies at which they use echolocation, being 45khz and 55khz respectively. Both of these frequencies are well out of the range of human adult hearing which usually rolls off at less than 20khz (unless you have had a misspent youth mixing pop groups in which case you will be lucky if you can hear above around 12khz!).
Bats are also one of the many groups (i.e. virtually everything except birds) that are massively under-recorded on Islay - so if there is someone out there who fancies becoming Batman (or Batwoman), then please get in touch.
Photo - Hugh Clark - The Bat Conservation Trust