Nest Boxes

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Barn Owl Nest Box

The barn owl is white beneath and golden-brown or buff on top, with a heart-shaped monkey face and black eyes. It hunts over rough grassland and will not nest unless there are plenty of voles nearby. Boxes provide essential roosting places as well as nest sites.

The best place is a quiet, undisturbed building away from busy roads, although boxes placed on large trees will also be used. A box like a tea chest or packing case is ideal, but strong, weatherproof plywood lasts much longer than a soft tea chest. The box should be at least 460mm x 460mm x 610mm, but the bigger the better. The entrance hole should be 230mm square or more.

The box should have a lipped tray at the front to let young owls walk out of the nest. It can be fixed to a beam or wall by brackets or strong nails in a dark corner away from the building doorway. It is vital that there is a permanently open window or doorway you must be certain that owls will not be trapped inside the building or shut out from their young. Barn owls are specially protected by law, and occupied nests even your box should not be visited without a licence.

Owls are territorial nesters and boxes should not be put up close together.

Tawny Owl Box

Tawny owls are much bigger, red-brown or grey-brown owls, with large black eyes. They are the ones that hoot and make loud, sharp cries after dark, in woods, parks and even very large gardens with trees. The box is most useful in an area where a known nest site has been felled or blown down.

The best box is a chimney-style box made to mimic the hollow, rotten end of a broken branch. These may be surprisingly narrow and deep but the best box is of internal dimensions around 795mm x 230mm x 230mm, open at the upper end.

The box can be fixed at an angle of 45° in a large tree fork, or slung beneath a sloping branch, or fixed by an angled strip of wood to a vertical trunk. Drill a dozen 5mm drainage holes in the bottom and spread wood chips or stone chippings inside. Tawny owls also take readily to boxes made for kestrels.

Kestrel Nest Box

Kestrels are falcons that usually eat voles, mice and beetles, although town kestrels may live mostly on small birds. These are pigeon-sized but longer-winged, with long, narrow tails that may be broadly fanned as they hover in mid-air, looking for prey.

They may nest in tree holes, on cliff ledges or on buildings. The box should be large and solid, of 19mm or 22mm or 9mm exterior ply, with a perch across the entrance made from a small branch. It can be fixed directly to the side of a tree or in a large fork, at least 6m high, or on top of a tall, secure pole. It must be free from disturbance, in an area where nobody will interfere with the young birds. The entrance must have a wide, open space for good visibility and easy access for the birds. Drill some 5mm drainage holes in the floor and spread wood chips or straw over it. Check the box once the breeding season is over and replace the floor if it shows signs of rotting. Clean out the accumulated debris to open up the drainage holes.

Open-fronted Nest Box

This standard box design may be used by stock doves, jackdaws and little owls.

Stock doves are medium-sized, attractive blue-grey pigeons, smaller and bluer than woodpigeons, without the white neck and wing patches and rarely in such large flocks. They nest in old parkland trees, derelict buildings and on cliff ledges.

Jackdaws are small, grey-black crows, with shiny black caps and grey on the neck. They like town parks and old woodland, and feed in open places. They are also happy to have a cluster of boxes close together (most other birds prefer to nest alone).

Little owls are the smallest British owls. They are brown with a fierce face and yellow eyes, and live in farmland and parks.

The box is like a very large garden box used by tits, but instead of a round hole, a large, square opening is best (see Figure). Fix the box with the entrance angled slightly downwards to give shelter from rain, wind and strong sun. Make sure it is very secure on a suitable tree, pole or wall.

Where to site a nest box

Boxes for tits, sparrows or starlings should be fixed two to five metres up a tree or wall, out of the reach of cats and curious humans! Unless there are trees or buildings, which give permanent shelter, it is best facing between north and east, thus avoiding strong sunlight and the wettest winds. Tilt the box forward slightly so that any driving rain will hit the roof and bounce clear. House sparrows and starlings will readily use nest boxes placed high up under the eaves and these will often deter the birds from nesting in your roof! Keep these away from areas where house martins normally nest. Open-fronted boxes for robins and wrens need to be low down, well hidden in vegetations.

Fixing your nest box with nails may damage the tree. It is better to attach it with wire around the trunk or branch. Use a piece of hose or section of car tyre around the wire to prevent damage to the tree (one of our visitors has recommended recycling an old cam belt). Remember that trees grow in girth as well as height, and check any fixing every two or three years.

Two boxes of the same kind may both be occupied if they are at the edge of adjoining territories and if there is plenty of natural food. Tits can, however, be very aggressive and seldom nest at densities greater than two or three pairs per acre. If you put up different boxes, you can attract several species.

Nest box maintenance

The nests of most birds harbour fleas and other parasites, which remain to infest young birds that hatch the following year. We recommend that old nests be removed in October or November. Use boiling water to kill any remaining parasites. Insecticides and flea powders must not be used.

If there are unhatched eggs in the box, these may be removed legally only between 1 August and 31 January, and must be disposed of.

If you place a small handful of clean hay or wood shavings (not straw) in the box once it is thoroughly dry after cleaning, it may be used during the winter by small mammals or birds for hibernating or roosting in respectively.