I've noticed a lot of bats around my house recently. I'd love to know what type of bat they are but all I see is a silhouetted glimpse as they dart past. Is there anyway to identify what types of bat(s) they are?
I absolutely love bats and always have.
In the UK we have eighteen species of bat. The Bat Conservation have a nice list for all the common UK species, including those which breed in the UK (which is 17 out of the 18 species, so we're doing quite well!).
The above link also has a recording of the noise each bat makes, which should help you work out the species you have near you as Wales is home to 15 out of the 18 bat species.
The Pipistrelle is the most common UK bat:
Pipistrelles are the commonest British bats, weighing around 5 grams (less than a £1 coin). A single pipistrelle can eat 3,000 tiny insects in just one night!
They also don't have any qualms about flying around your head for insects, which they used to do outside my old house. They have a wingspan of 190-235mm, which would fit a young pipistrelle having a 4inch wingspan. However this is only a most likely option.
The Natural History Museum provides a decent PDF of British bats which has some details of each bat, again this should help with the distinction.
The best way to identify bats in flight is to use a bat detector. This is a device with a microphone that listens to the bats high frequency calls, and plays them back at a lower frequency.
Bats use echolocation calls to find out what is around them. For most UK bats, these are typically between 30KHz and 80KHz. So they are not audible to humans. Different species of bats call at different frequencies, and they sound different, often 'clicking' or 'flapping' noises. Using a bat detector, you can hear what frequencies they are calling at, and figure out what species it is.
Pipistrelle bats are the most common in the UK, though note there are actually several different species of pipistrelle. Common pipistrelle and Soprano pipistrelle are very similar, the easiest way to distinguish them is the Soprano has a higher frequency call.
You can buy a bat detector for about £50 or so. A popular model is the Magenta Bat 4 or Bat 5, these are simple to use and reliable. Or there are cheaper options using electronic kits, though they may require some work to solder and put it together.