In 2016 I arranged for a gentleman from the NSW Department of Primary Industries, Dr Leroy Gonsalves, to come and talk to us at Permaculture Sydney West about microbats. Biodiversity is always a great subject for a PSW meeting, plus I personally knew nothing about microbats and wanted to learn.
As I expected the talk was fascinating. One of the points Dr Gonsalves made was that with land clearing and urbanisation of the Sydney basin, microbat habitat was declining at a serious rate. As a direct result of his comments I went out and bought a bat roosting box, closely followed by a second, and just recently I made and installed a third.
At this point in my article I would normally go through what microbats do for us (they eat insects, including mosquitoes) and how they fit into the local environment. However, rather than regurgitating somebody else’s research, the site Backyard Buddies provides lots of information on these creatures - Microbat - Backyard Buddies. Also, details (including photos) of the almost 20 microbat species that make the Sydney basin their home can be found here - meet sydney's microbats (ausbats.org.au).
The Two Commercial Bat Boxes
The first one I bought was as a kit (the second was too) that I was able to put together and then paint up so that it didn’t stand out quite so much (I used a nice British Racing Green colour). As usual for me, I can’t remember where I actually bought the kits from, but when I looked on the ‘net, the only place that was selling bat boxes that looked like mine was FauNature - Bat Box - fauNature
The measurements of the boxes are -
- the back board is 500mm x 190mm
- The bat box itself is 310mm long x 190mm wide by 100mm deep
- They are constructed from 18mm plwood
- The access is through a 15mm gap in the bottom of the box.
There is also a divider that goes up the inside middle of the box that has a coarse hessian glued to each side to help the bats get access. The inside of the front and back of the box also have coarse hessian glued to them. The bottom part of the backing board directly under the access gap has some grooves cut in it longitudinally to also help the microbats get into the box. To affix them to our front trees I put some coach bolts into the trees through the holes provided.
To site the boxes, the literature seems to recommend that you have a number of boxes facing different directions so that the bats can choose which one suits their needs for that time of year. Consequently the first bat box was mounted facing north, while the second on was facing east. Both boxes are mounted 2.5m to 3m off the ground on the melaleuca alternifolia tree at the front of our property. Also, within about 5m to 10m of the boxes is a self-watering birdbath and a self-watering insect watering station if they need a drink of water.
One of the questions I get asked is, “do you get microbats in your bat boxes?” and the honest answer is – “I don’t know”! They are small and nocturnal so I don’t see them flitting around. There are certainly marks on the grooved access area that lead me to believe they have been tenanted, but it is difficult to know at any particular time if bat(s) are in residence.
I have been reluctant to unscrew the front hinged door (secured by two screws) to find out one way or the other. Until recently. I climbed up a ladder, unscrewed and opened the door, and found that they were indeed tenanted, just not by what I was expecting (see photo below!). I have asked for advice from experts as to whether they are a problem for the microbats or not, and it turns out that while these spiders will not predate the microbats, they are likely to put them off roosting in the bat boxes! I know they certainly would put me off, so I need to evict them.
The third Bat Box
I decided I wanted to build my own this time, so I could have a west facing bat box as well as the other two. My source of information was the wonderful book ‘Nest Boxes for Wildlife’ by Alan and Stacey Franks. There are two bat box designs and the first one I settled on was on pages 44 and 45 of the book. It states that it should be constructed of ‘rough sawn hardwood’ and this proved to be difficult to get hold of. Hardware stores and even timber merchants in my area seemed to only have DAR timber and when I asked about rough sawn they just gave me a strange look. I was able to find some in the delivery of fire wood we had delivered, but the dimensions of the pieces would not give me enough timber to build what I wanted.
Raw materials!
Fortunately, on page 46 was a different design where it stated that “the dimensions may be varied to almost any size” so that sounded good to me! It was basically a bottomless box with the cut-off leg of a pair of jeans attached inside. This would allow the microbats to climb up inside and find shelter. The idea was also to chain it below a limb of a tree rather than screw it into the tree itself.
Backing board completed
I was able to souvenir some rough sawn hardwood timber from the wood heap and by putting two pieces together was able to construct a backing board that was 590mm long x 220mm wide x 35mm thick. It was a bit heavier than I intended, but you work with what you have! I also used sides and the top from the wood heap, the sides being 460mm long x 100mm wide x 20mm thick and the top is 190mm wide x 140mm deep x 12mm thick. I also cannibalised a tomato stake to use as reinforcing to help with attaching the sides to the back board. The front of the box was a bit more difficult because I had no firewood the right size, so I found an old piece of pine and cut it to size – 500mm long x 140mm wide x 20mm thick. All the parts were fastened together with screws. It was the just a case of removing the leg from an old pair of jeans and screwing it in to one side of the top of the box.
Walls up and secured
Fabric installed
Closeup of fabric attachment
With the box finished I was able to hang it from one of the melaleuca alternifolia trees in the front yard that faced roughly west. I found a couple of cup hooks and screwed them into the sides of the backing board, then cut some old chain to length and looped it over the branch, where it hangs about 2.5 metres above the ground.
Now it is just a case of waiting to see if I can find any evidence of use by my microbatty friends!
For our overseas friends -
It appears that New Zealand has two species of microbats, learn more here - New Zealend Geographic on Microbats
The UK has 18 species of bats and they all appear to be microbats - UK Bats.org - types of bats
Canada has 3 species of microbats - Wildlife Preseration Canada on Microbats
