Should I Put Anything in My Bird Box?

No, not for a normal UK garden bird box used for nesting. Leave the inside clean and unlined. Birds choose and arrange their own nesting material. The exception is a small amount of suitable material put in a clean box for winter roosting, rather than to build a nest for them.

Should I add bedding or nesting material?

The British Trust for Ornithology (BTO) nest-box guide says there is no need to line a box. Adding a ready-made nest of grass, cotton wool or toy stuffing is unnecessary. The bird needs to choose material suited to its own nest.

No need to put nesting material directly in the nestbox, as the birds will prefer to do this themselves.

Do not offer pet hair: the RSPB warns that flea or worm treatments can leave harmful chemicals on it. Keep string and twine out of the box too; they are not needed to prepare it for nesting.

How can I help the birds instead?

Leave a little natural moss or dry grass in the garden where birds can collect it themselves, as the RSPB suggests. Choose a box made for the birds you hope to attract: a robin needs a different entrance from a blue tit, for example. The BTO guide explains common box types and placement. A suitable, dry, well-placed box helps more than filling it with bedding.

What about an old nest or winter shelter?

Once you are sure the box is no longer in use, the RSPB recommends clearing out old nests in autumn, wearing gloves, rinsing with boiling water and letting the box dry. Avoid insecticides. Never open or clean a box with an active nest. If you missed autumn cleaning and it is already February, the RSPB advises leaving the box rather than risk disturbing birds.

For winter roosting, the RSPB says you may put a small handful of clean hay or wood shavings in a cleaned, dry box; it advises against straw. That is an optional winter measure, not a reason to pack a breeding box with nesting material.

Related reading: Where Do Birds Go at Night? A UK Garden Guide; How to attract birds to your garden: five practical tips.