Nest boxes for birds

The Birder's Market | Resource | Garden Birds |  Nest boxes for birds

Tit boxes
Tit boxes
Owl boxes
Owl boxes
Open fronted (flycatcher or robin)
Open fronted (flycatcher or robin)
Special boxes
Special boxes
Making a nestbox

Making a nestbox

Advice from the RSPB
Natural nest holes do not come in standard sizes, so use these dimensions only as a guide. Any plank or sheet of about 15 mm thick weatherproof timber is suitable. However, do not use CCA pressure-treated timber, since the leachates may harm birds.
Cut each section as per the RSPB plan, which you can download free by simply clicking on this link

The plan gives measurements for a small and a large box. Use only the first or the second figure throughout. For starlings and great spotted woodpeckers, use the dimensions for the large box; all the others need the small one.

The bottom of the entrance hole must be at least 125 mm from the floor. If it's less, young birds might fall out or be scooped out by a cat. The inside wall below the entrance hole should be rough to help the young birds to clamber up when it's time for them to leave.

Putting it together

Drill drainage holes to the base of the box, and use galvanised nails or screws to assemble. It's always best to leave the box untreated. As it weathers, it will blend into its surroundings. Softwood boxes can be treated with selected water-based preservatives, which are known to be safe for animals, such as Sadolin. Apply it only to the outside of the box, and not around the entrance hole. Make sure the box dries and airs thoroughly before you put it up.

A woodpecker box should be filled with a block of balsa wood, rotting log or wood chips – woodpeckers like to excavate their own nesting cavities.

Do not nail down the lid, since you will need to clean out the box in the autumn. Attach the lid with a brass or a plastic hinge that will not rust, or hinge it with a strip of leather or rubber (an old piece of bicycle inner tube will do). Fasten it down with a good catch.

How big does the hole need to be?

The entrance hole size depends on the species you hope to attract:

25 mm for blue, coal and marsh tits
28 mm for great tits, tree sparrows and pied flycatchers
32 mm for house sparrows and nuthatches
45 mm for starlings
The small box with 100 mm high open front may attract robins or pied wagtails. A wren would need a 140 mm high front panel, while spotted flycatchers prefer a low 60 mm front to the box.

Siting a nestbox

Siting a nestbox

This depends on the species the box is intended for. Boxes for tits, sparrows or starlings should be fixed two to four metres up a tree or a wall.

Unless there are trees or buildings which shade the box during the day, face the box between north and east, thus avoiding strong sunlight and the wettest winds.
Make sure that the birds have a clear flight path to the nest without any clutter directly in front of the entrance. Tilt the box forward slightly so that any driving rain will hit the roof and bounce clear.
House sparrows and starlings will readily use nestboxes placed high up under the eaves. Since these birds nest in loose colonies, two or three can be sited spaced out on the same side of the house. Keep these away from areas where house martins normally nest.
Open-fronted boxes for robins and wrens need to be low down, below 2m, well hidden in vegetation. Those for spotted flycatchers (right) need to be 2-4m high, sheltered by vegetation but with a clear outlook. Woodpecker boxes need to be 3-5m high on a tree trunk with a clear flight path and away from disturbance.

Fixing your nestbox

Fixing your nestbox

Fixing your nestbox with nails may damage the tree. It is better to attach it either with a nylon bolt or 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. Remember that trees grow in girth as well as height, and check the fixing every two or three years.

Two boxes close together may be occupied by the same species if they are at the edge of adjoining territories and there is plenty of natural food. While this readily happens in the countryside, it is rare in gardens, where you normally can only expect one nesting pair of any one species. The exceptions to this are house and tree sparrows and house martins, which are colonial nesters. By putting up different boxes, several species can be attracted.

Nestboxes are best put up during the autumn. Many birds will enter nestboxes during the autumn and winter, looking for a suitable place to roost or perhaps to feed. They often use the same boxes for nesting the following spring. Tits will not seriously investigate nesting sites until February or March.

Cleaning nestboxes

Cleaning nestboxes

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 the autumn, from August onwards once the birds have stopped using the box.
Use boiling water to kill any remaining parasites, and let the box dry out thoroughly before replacing the lid. Insecticides and flea powders must not be used.

Unhatched eggs in the box, can only be removed legally between August and January - and must then 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, small mammals may hibernate there, or birds may use it as a roost site.
It is quite normal for a few eggs to fail to hatch, or for some young to die. Blue and great tits (right) lay up to 14 eggs to allow for such losses. Cold weather and food shortage may lead to nest desertion, or to only the strongest young surviving. The death of one parent or interference from animals or humans may also cause desertion.
Avoid inspecting nestboxes in use, however tempting it may be to take a peek! Simply watch and enjoy from a distance. Only open it up if you've got appropriate skills and experience and are taking part in a monitoring project, such as the BTO’s Nest Record Scheme.If you want to see the chicks as they grow, you could consider installing a nestbox camera before the breeding season starts.

The Birder's Market | Resource | Garden Birds |  Nest boxes for birds

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