Designing a nestbox
Birds are different sizes, but will use 'standard' boxes, if you change the size of the entrance hole to suit them. Blue Tits and Great Tits are most likely to use these.
With a large front opening, this box is used by birds that nest in cracks and among creepers, such as Robins, Wrens and Spotted Flycatchers.
Making a box
Use solid wood or exterior-grade plywood, about 1.5cm thick. Thin wood is not weather-proof and most other materials will not last long outdoors.
Use nails, screws or weather-proof glue to join the pieces together.
Decide the size of the entrance hole.
Use a brace and bit, a holesaw or a fretsaw to make the hole.
A new box will show up to predators and vandals. Paint it with a modern preservative stain which is non-toxic.
Warning: Do not use creosote!
Beat the weather
Shade the box from the sun, especially if it is on a wall. The box should face north or east in order to face the entrance away from the worst of the wind and rain.
Tilt the box slightly forward to keep water away from the hole.
Table manners
Nestboxes near bird tables are not a good idea. Birds trying to nest are disturbed by those that come to feed.
It is best not to feed birds during the nesting season - Natural food is better for them and their young.
For tits, the box must be no more than 30 metres away from trees where they can collect insects for their young.
Warning: Keep boxes away from places where cats can reach!

Nestbox Hole Diameters