A better mousetrap

Many years ago I made a humane mousetrap ago because my family don't like the idea of the spring "snap" trap. I don't really either, partly because when I was a kid my father used one and I saw plenty of mice that had not been killed cleanly . Besides, I just like making things.

This trap is pretty old now and no longer works reliably, but it's given good service and in the 15 years or so it's been used, it's caught probably over a hundred mice. However, the old design was over complex and a bit tricky to set. It had a drop-down door held open by a thin bolt that was withdrawn by the mouse walking over a see-saw. Setting it was always a balancing act between having it trigger by itself or not having it trigger at all. I thought I could do better.

The old trap showing signs of wear, and being eaten

The new design has a pivoted door, is simpler, smaller and seems to work well, so I'm describing here how to make one.

The new one is much smaller!

Here's the schematic:

The trap is a simple box - two sides, base and back - with a hinged door and hinged wire mesh on top. The top could be another piece of ply, but the mesh lets you see into the trap when the door is closed. The top needs to be able to open so the see-saw can be removed for cleaning - it's essential that mouse droppings are removed from under the see-saw or it will not "rock" properly.

The materials were chosen from scraps I had lying around (I hate throwing away offcuts). The carcass of the box is made from 9mm plywood, and the see-saw and door from 5mm ply. Neither of these thickness are critical although the mesh is hinged with small staples in the top of the back, so this cannot be much less than 9mm. If you do change the thickness of any pieces, check that this hasn't changed any of the other dimensions.

The box carcass (sides, back, base) should be simply glued together with wood glue.

Cut the see-saw so that it fits inside the box with about 1mm clearance from the back and sides. Fit the wire door support next. It's a square hoop that the door rests on when open. I made this and all the other wire pieces from some 1.6mm galvanised wire I already had, just pushed into holes drilled with a 1.5mm drill bit. This was a bit lucky - the combination of bit size and wire size meant that the wire is held firmly in the hole without anything else being needed. You may need to search around to find something suitable. Thin coat hanger wire may work.

With the door support in place, find the balance point of the see-saw by placing something suitable under it. Then mark the position for the screws as 2-3mm back from this balance point, so that the see-saw will naturally rest forward but will tip back with the weight of a mouse. Place the see-saw in the box as shown in the diagram, and check it balances easily on the screws and doesn't touch the sides, then press firmly down on it so the screw make indentations in the base. Don't press too hard - you are just trying to make indents so that the see-saw will easily locate itself when you put it back after cleaning.

Drill holes in the sides for the door pivots - make sure that the pivot line is at right angles to the sides or the door will catch against the sides. Hold the door in the right position and then push wire through the holes on each side so that they mark the door where holes should be drilled. The holes in the door should be wider than the wire so the door swings freely. You can see from one of the picture that my door is sloping slightly backwards because it's fractionally longer than the opening. This actually works well - you don't want the door to be able to be completely vertical as it could be pushed open.

Once the door is in place, bend the door support as needed so that the door just rests on the wire when the see-saw is at rest (forward), and closes when the see-saw is tipped. You will need to fiddle around with this to get it just holding the door open so that the slightest movement of the see-saw will release it.

Cut some wire mesh to cover the top and loosely staple to the top of the back so that it can hinge back to give access to the inside. Drill holes in the top of the sides to take wire turn catches to hold the mesh in place.

Finally you should seal the inside with water-based varnish. Mice will make it wet and messy when they're inside.

For bait you don't need anything special - contrary to popular opinion, mice don't have any special preference for cheese. I just use a few crumbs of digestive biscuit.

I release the mice a little way away from the house so I can be sure they don't come back. I've no idea if they are likely to, but I did read a comment left by someone who had bought a humane trap. They were complaining that it was useless because the mouse kept returning. This person didn't seem to consider that they may all have been different! In my experience it's normal that you don't just have one mouse -  "catch one, catch more".

That's it. I hope it's useful.

Good day's foraging

Mushrooms are late this year. A visit to the New Forest at the beginning of October drew a complete blank. Maybe the wet weather at the end of September has at last encouraged them to show - the profusion of Sulphur Tufts and Brown Roll Rims in my garden would suggest so. I spent a few days searching around my local woods in Warwickshire for something edible, and after drawing a few blanks, eventually this morning came up trumps.

Shaggy Parasols, Horse mushrooms (or maybe the similar Agaricus macrosporus), Wood Blewits and Oyster Mushrooms - and some Sweet Chestnuts. Shaggy Parasols can apparently cause stomach upsets in some people - fortunately no-one in my family.

A wild mushroom risotto is already on the menu!

Building a barn owl box (2)

The box is complete! The photos below record the process of construction as it happened...

The front with cut-outs. Ideally the piece cut out for inspection panel could be used for the panel itself, but unless you're very neat and the saw blade very fine then the piece cut out will not fit tightly enough. I had to discard it and cut a new one. Not a problem as there's plenty remaining from the sheet.

The front with top and side battens. The length of the side battens is such that there is 2cm beneath the base when fitted.

The back with battens in place. The centre batten is to provide strengthening - the box will be attached to a tree via a substantial batten (1.5" x 3") which is bolted to the back of the box.

The side battens deliberately overlap the top corners of the inspection hatch. Along with a retaining piece on the lower edge this is what's intended to stop the panel falling into the box. I decided to overlap the panel all the way so there would be no light leakage into the box...

... the edging was done using pieces cut from the remaining plywood. The side pieces are not yet in place here.

The back with sides attached.

The front in place. It's flush at the bottom and recessed 4" at the top.

With top attached.

A view of the bottom. The base is left until the end to allow easy access for fitting the inspection panel.

The shelf in place. A couple of wedges help to make it firm...

...as shown here.

The back of the inspection panel. The original plans use some pieces of wood on the outside of the front to hold the panel in place, but I thought they might be liable to getting wet and rotting (because the end-grain is upright) and so put some lugs on the inside instead.

The lugs are just bits of waste plywood that fit over the lip of the hatch opening.

The base with drain holes. The base needs to be planed to fit, including bevelling the ends slightly to match the slope of the sides.

The box completed! The battens on the back (and where they fix to the sides) are glued as well as screwed since all the weight of the box is carried here. Use glue sparingly (wood glue, waterproof) so it doesn't spread inside the box.

The box will be treated on the outside (only) with a few coats of water-based preservative. I use Cuprinol Ultimate Green, partly due to availability and partly a personal choice of colour. It's one of the expensive 5-year treatments but hopefully worth it. Solvent-based preservatives are generally more effective but definitely not recommended for bird boxes.

Now I'm just waiting for some roofing felt to put on the top....

Eventually it turned up. The finished box:

That's it!

Building a barn owl box

I don't remember what gave me the idea of building owl nest boxes. Maybe it was after visiting a rather sad owl sanctuary in the west country which my wife Jill was really uncomfortable with (although I was able to get some good owl photos), possibly this made me realise that we no longer have owls around where I live. Anyway, I decided to make a Tawny owl box (Dutch letterbox design) and the local council kindly agreed to put it in a nearby field that they own. That led to my being asked if I'd like to made some Barn owl boxes for them, and so I agreed.

I looked around on the Internet for a suitable design. The simplest type is the A-frame, but I don't really like this because the bottom corners seem wasted space, unusable by the owls and places where all manner of crud will accumulate. The Barn Owl Trust has what looks to be a well designed box and that's what I'm making. As well as providing plans, their website also contains step-by-step pictures of construction which are very helpful but probably don't contain everything you need to know. At least one thing not covered is how to lay out and cut the pieces needed from a single sheet of plywood, and so I've had to do this myself as shown below.

Cut all the pieces out. I normally like to use a panel saw for woodworking but I decided a jigsaw would give a cleaner (and thinner) cut. The cut edges can be cleaned up with a plane. Eventually some of the edges will need to be bevelled a bit (top of sides, front and back, and the ends of the base. This will be evident when you assemble the box.


The notes on the diagram above give a few tips, including how to cut out the front and back trapezoids without resorting to Pythogras!