Knowledge base: Nest boxes and nesting birds
When should I put up a nest box?
Before the breeding season, so autumn and winter are fine. The BTO says nest boxes for small birds are “traditionally” put up in spring, notes that pairs start prospecting for sites in late February, and adds that boxes can also be used for roosting in winter, so a box up early is not wasted.
Why earlier helps
A box that is already on the wall when pairs start looking in late February is in the running. A box up by autumn can also give shelter on winter nights, which the BTO mentions as a second use.
Getting the box right
The BTO’s buying advice is:
- Wooden walls at least 15mm thick, and an insulating material such as wood or a wood and concrete mix rather than metal or ceramic.
- A floor of at least 130 square centimetres, because birds may lay fewer eggs in smaller boxes.
- No perch. The BTO says perches are unnecessary and can give squirrels or weasels a foothold.
- A way to open it so you can clear out old nest material at the end of the season.
- Not built into a bird table, since feeding and nesting birds may conflict.
Hole size decides who moves in; see what size hole does a nest box need? Siting is in which way should a nest box face?
Once birds move in
Leave it alone. An active nest is protected by law; see can I remove a bird’s nest?
Sources
- BTO: Putting up a nest box, opened 14 November 2026.
- BTO: Buying a nest box, opened 14 November 2026.