Information provided by RSPB
Watching a bat flit across the evening sky is a pretty special and magical experience. Sadly, bats are in decline across the UK, largely driven by a gradual loss of habitat. You have the power to help your local bats by providing them a safe place to roost, raise their pups and sleep during the day – build a bat box! Here’s how.
Overview
Estimated time: 3 – 4 hours
Season: all year
What you’ll need:
- Ready-made bat box, or untreated rough-sawn wood 15cm wide x 1.1m long x 1.5cm thick or more
- Ladder
- Drill
- Screws
- Saw
- Nails
Instructions
The basic principles of a bat box
They should be made from untreated wood – wood that has not been pressure-treated with chemicals. Bats are sensitive to smells and preservative chemicals may be harmful to them. You will probably need to go to a saw yard rather than a timber merchant, as you’re unlikely to find it at a DIY store. Make sure you look for the Forest Stewardship Council (FSC) logo.
The bat box should also be made from rough-sawn wood (rather than smooth, planed wood). If your wood feels too smooth, roughen it by dragging the teeth of a saw across the surface – this helps bats get a good grip as they clamber around their new home. Your box will also need to have good, tight joints – bats hate a draught!
It’ll need a narrow slit at the back of the box, with a rough piece of wood leading up to it that they can clamber up. The very best bat box is one with two or more internal compartments, and one that is as large as possible – a deep cavern makes bats feel really safe and keeps the air temperature more constant.
The dimensions shown are for 20mm thick wood. If your wood is different to that, the dimensions of the Base should be 150mm by 130mm minus 2 x thickness of the wood. E.g. if the wood is 18mm thick, the base should be 150mm x 94mm.
Building your bat box
You’ll need a sheet of timber 15cm wide by at least 1.1m long, as thick as possible to keep the bats insulated from too much cold and heat inside (ideally 1.5cm or more).
Mark the wood with a pencil, according to the diagram, and then cut it in to the sections. Nail all the pieces together as shown in the diagram, making the joints as airtight as possible.
Choose your location
You could put it under the eaves of your house or, if you have a large garden, on the trunk of a mature tree. Look for a spot that is at least 3m (10 feet) from the ground, sheltered from strong winds and exposed to the sun for part of the day.
Position your box so it faces between southwest and southeast. Make sure there is a clear flight line in. Some foliage around the box will encourage use, such as climbing rose or honeysuckle.
Now put your bat box up
Drill holes at the top and bottom of the backing plate and fix to the wall with screws or plugs. If you’re fixing it to a tree, you can use adjustable ties so you don’t cause any damage to the tree. If you don’t have these, use stainless or galvanised screws or nails.
Watch and enjoy!
All bats and their homes are protected by law, so it’s important you don’t disturb them. Watch and enjoy from a distance. If you don’t see any bats going in or out, look out for their black droppings underneath the entrance. They’re little dry pellets that crumble to dust.
What to look out for
We’re lucky to have 18 species of bat in the UK, but there are a few usual suspects that we’re most likely to see in our gardens:
- Noctules are the biggest bats in Britain. They have long, narrow wings, and a high and straight flightpath.
- Daubenton’s bats are medium-sized bats with a white underside. They often fly low over water and use their big feet to scoop insects from the surface. They’re also one of our Species on the Edge target species!
- Common and soprano pipistrelles are Britain’s smallest species of bat, weighing the same as just 10 paperclips! They look much bigger in flight and have a very erratic flightpath. They are the most common bats seen in gardens and the most likely to use our bat boxes. These Pipistrelles are also Species on the Edge target species.
If you think you see one of our Species on the Edge target bat species – brown long-eared, Daubenton’s, common pipistrelle and soprano pipistrelle – be sure to let us know! Email sote@nature.scot
