Weekend Projects – Nesting boxes

Wednesday 11 July 2018

Every self-respecting garden needs a bird box and you can make your own quite easily with a few tools. The important thing is to make sure it is right for the birds you want to attract to your garden. The place to go for that information is the RSPB – Royal Society for the Protection of Birds – website – www.rspb.org.uk. I decided to make two nesting boxes: one for blue, coal or marsh tits with a 25mm diameter hole and a slightly smaller box with an open front for wrens, as we do see them briefly each year flitting through our garden. There are certain specifics you need to observe: the correct hole size, no peg on the front as predators will use it to get at the nest and the hole high enough above the bottom for the same reason. On the RSPB’s website, search for ‘making a nestbox’ for more information.


The first step is to mark out the front of the box on some sawn, untreated softwood. The RSPB recommend 15mm-thick board but I used 19mm, which I think is acceptable. I used a ring shape measuring 25mm in diameter to mark the entrance hole. This had to be 125mm minimum above floor level for the safety of the eggs or chicks.


Use a sliding bevel to mark out the roof angle, which is about 45°. Use a quick clamp to hold the board on the bench top while hand sawing the roof profile.


Having cut one piece, you can now mark out the back piece using the front one to get it the same size and shape. After that, cut it out in order to give you a matching pair.


The entrance hole needs to be drilled using a ‘sacrificial board’ underneath for the flatbit tip to go into as it breaks through. This also helps to limit the breakout in the back of the board.


On the reverse of the front board a series of very shallow saw cuts or kerfs will give fledgling birds something to grip on to when they try to make their first effort at flying.


The boards on the sides need to be sawn a bit narrower by the width of the front and back board combined. Clamp the boards to the workbench top for rip sawing ‘with the grain’ to a marked pencil line.


The wren nestbox needs to be a bit smaller – wrens are tiny and they need a ledge to fly from. You don’t want the opening to be very big as predators could potentially attack the nest.


The boards for the sides have their roof angle marked directly off the front board. Next, mark a line with a set square along the face so there is a complete line to saw along.


The front and back boards need to be drilled, countersunk and screwed to the sides. Even setting the screws in from the end won’t prevent splitting – as you can see here, the screw head has started to part the wood fibres.


Because softwood has a tendency to bow after it has been machined, it may be necessary to pull the last side outwards slightly before screwing it in place.


The bottom needs to be cut for a nice neat fit; this can only be really accurately done once the basic nest box shape has been put together.


If the box is slightly out of square, clamping across the opposing corners will pull it gently back into shape so the bottom can be tapped into place and screwed through the middle of each side.


Next, draw lines from corner to corner to position where the drain holes need to be so the nest can stay dry. Since screws are in the middle of each side, they don’t conflict with the drilled holes.


An alternative is to use galvanised nails to assemble your bird box. I used screws for the wren box and nails for the larger one. To avoid splitting, don’t place the nails near the end of the board.


The exterior finish must be ‘bird safe’, i.e. a low VOC – Volatile Organic Compound – water-based finish that can’t harm birds or other wildlife.


I decided to fix one half of each roof and hinge the other part. For this, standard FE – Far Eastern – ply is tough enough to resist the elements. Once sawn, the edges need planing to smooth them.


The wren box may present problems as the triangle piece under the roof front is hard to fix. I used long panel pins and clamped the triangle under the roof before pinning.


The simplest hinge is a strip of fabric cut and glued with contact adhesive over the apex of the roof. Next, make a roof covering out of flashing roll, which is used for roof repairs. It is easy to cut and is self-adhesive.


The completed bird nesting boxes should look something like these.


1. When you use a chisel or plane for the first time, it needs to be made really sharp. I use a diamond honing plate, which is a really good investment. The back of the blade is flatted on the very 1,000 mesh side of the plate using lapping fluid as the lubricant.

2. Now it is turned over and the honing guide it is fitted in guarantees the correct sharpening angle, which is shown on the side of the guide. A few back and forth strokes should give a good sharp edge to plane with.