Best bird nest boxes

Nest boxes can be an excellent substitute for the holes found in old trees or dilapidated buildings that cavity-nesting birds, such as tits and sparrows, prefer.

But in recent years, bird-welfare organisations have raised concerns about the design and materials used for some of the bird boxes on sale. They warn that novelty and fashionable boxes might not provide the best welfare features for birds.

So, we wanted to help you sift through the many products available and navigate you towards the designs that may help small garden birds have the best chance of breeding successfully. Plus, we also reveal the bird boxes we don't recommend. 

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Best boxes for nesting birds

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What to look for in a bird box

Materials 

The best materials for bird nest boxes are harder types of wood, such as cedar, oak or beech, at least 15mm thick, or woodcrete (a waterproof mixture of wood fibres and concrete). These provide good insulation and are difficult for predators to gnaw through to get to a nest. 

Avoid metal, ceramic, plastic or resin boxes with thin walls that don’t provide insulation and can become too hot or too cold for chicks to survive. These impermeable materials can also cause condensation inside a box, creating damp and unhealthy conditions. 

Body 

Birds will stay cosy in a box with good wind and waterproof joints between the sides. Look for a box with the wood grain running vertically the length of the sides, rather than horizontally. This encourages water to run off the wood and reduces the chance of it penetrating the end grain, which can lead to dampness and rotting. 

It’s helpful to avoid the back of the box sitting fully against a tree trunk where it can be dampened by rain running down the surface. Some boxes have wood or rubber battens for mounting the box which help. 

Entrance holes

The size of the hole determines which species of birds are able to use a nest box, with small holes excluding larger birds from nesting. Choose a hole 32mm across to give access to all our common small garden birds or a 25mm hole, if you prefer to restrict access to the smaller tit species and possibly tree sparrows. 

Look for a hole that is at least 120mm above the floor of the box. This is something that is often missing from the smaller, commercially available bird boxes. 

A hole that is too low will allow predators, such as cats, to reach in and take the nestlings. A metal plate around the hole can prevent woodpeckers and squirrels from enlarging it so that they can get inside. 

Roofs

A sloped roof can help rainwater to run off and discourage predators, such as cats, from sitting on top of the box, waiting for fledglings to emerge. 

Roofs that project over the sides will help to keep the whole box drier and a projecting front can also provide useful shelter from the elements over the entrance hole. It will also help to prevent predators from reaching down off the roof into the nest box. 

Perches and purchase points 

A perch isn’t necessary for small birds, and can provide squirrels and weasels with a foothold to reach into the box to grab eggs or chicks. Avoid protruding bases or other decorative features that could give a predator something to hang on to if they leap to reach your box. 

Access

Many bird-watchers like to keep an occasional eye on the progress of nests and this is easier to do if there's an access hatch in the roof, front or side of the box. 

It’s useful if you can get your whole hand into the box to pull out any old nesting material and this is usually viewed as a sign that the box is large enough for birds to nest in. 

Floor 

It's preferable if the floor isn’t flush with the bottom of the box, to prevent drips of water from the side of the box entering the end grain of the wooden base and making it damp. However, this is a rare feature on commercially produced boxes. Drainage holes will prevent a nest becoming waterlogged if water does manage to get in.

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Where to site your small-holed nest box

You’ll want to provide a safe and comfortable environment for the birds who use your nest box, protected from the weather and predators, such as squirrels and cats, and limiting aggressive competition from other birds. 

Small birds start to look for a nest site in the latter half of February, but some birds will use them to roost in winter, so putting up your nest box in late winter is ideal. However, it’s never too early to put up a nest box. 

• Small-holed boxes are best placed one to three metres above ground on tree trunks. If you don’t have trees in your garden, place your box on the side of a shed or wall. 
• Make sure it’s sheltered from the prevailing wind, rain and strong sunlight, and try to mount it with the front vertical or preferably slanted slightly forwards to prevent rain from getting in the box. 
• Give birds a clear line of sight to fly to the nest box, rather than obscuring it with foliage. The exception to this is open-fronted robin nest boxes; robins prefer them concealed behind thick, overhanging vegetation.
• Use galvanised or stainless-steel screws, or nails that resist rusting and regularly check it’s securely attached. 
• Don’t put nest boxes too close together or near bird feeders to avoid disturbance and competition between neighbours. 
• Site them out of reach of leaping predators such as squirrels and cats.  
• Rather than using nails to attach the box to a tree, the Wildlife Trusts recommends using rope or wire wrapped right around the box and trunk (remembering to protect the trunk from the wire cutting into it by using a piece of rubber underneath it).

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Cleaning your bird nest box

To prevent your bird nest box harbouring parasites including fleas, remove old nesting material in autumn and swill the box out with boiling water, then dry thoroughly before rehanging. 

Wear gloves and preferably clean your box outside using a dedicated cleaning utensil. To avoid transferring bird germs, don’t use the bird nest box cleaning kit for anything else and wash your hands thoroughly afterwards.

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