Buying a nest box

Commercially available nest boxes come in a huge range of shapes and sizes, but beware: while some provide a perfect breeding cavity for birds, others are far from ideal. Here are our guidelines to help you choose wisely and the retailer we recommend.

Great Tit. David Waistell — A pair of Great Tits using a Woodcrete nesting box by David Tipling

Choosing nestboxes — Nest boxes - the good and the bad

Only choose a box made from an insulating material such as wood or a special waterproof wood/concrete compound.
Don’t choose a box made from dense materials like metal or ceramics as the interior can become too hot or too cold for chicks to survive.
To provide insulation and be durable, the walls of wooden boxes should be at least 15mm thick. Wooden boxes can be safely treated on the outside with a preservative provided it is non-toxic and water-based. A box made from cedar, oak or beech will outlive one made from softwood such as pine.
Choose a box with a 32mm entrance hole as this is the ideal size for all small hole-nesting birds such as sparrows and tits. Choose a smaller 28 mm hole only if you want to restrict the box to Blue Tits.
The box should not be too small inside as birds may lay fewer eggs in smaller boxes. The internal floor area should at least 130 square centimetres (20 square inches).
Perches are not necessary and may even act as a foothold for squirrels or weasels as they reach into the box to grab eggs and chicks.
A good box should provide easy access for human observers who wish to record the contents and to clean out the disused nesting material at the end of the season. More on access and cleaning.
Don’t choose a box which is incorporated in a bird table as the nesting birds may come into conflict with the feeding ones.