Bird boxes

Your guide to garden nest boxes

Bird boxes are mainly used by birds in breeding season, as this is the time when birds will be looking for a suitable place to nest and lay their eggs.

Different sizes of nest-box suit different species of birds with very small boxes attracting wrens and treecreepers and largest ones attracting owls and ducks. The only maintenance a nest box will need is to remove old nest material as well as any parasites.

Nest boxes are usually wooden, though some varieties are made from concrete or mixtures of wood and concrete, called woodcrete. Some also have built in cameras for watching the activity of the nest boxes' occupants.

In terms of shape most are cuboid with a sloping roof. Many have a hinged top, side or front to provide access for cleaning or bird ringing. Boxes may either have an entrance hole or be open-fronted. Some nest boxes can be highly decorated and complex. Designs mimicking human house design or other structures are common in some gardens.

Types of nest boxes

There are two main types of nest boxes for gardens:

• Small-hole nest box for tit species
• Small open fronted nest box for Robins

Garden nest boxes are most commonly occupied by Blue Tits or Great Tits.

Try to get your nest boxes in position as early as possible, preferably at the beginning of January. Blue Tits and Great Tits may start looking around from mid February. Each year on St. Valentine's Day, 14th February, the British Trust for Ornithology (BTO) launches its National Nest Box Week, with the aim of encouraging people to put up nest boxes to help breeding birds and other wildlife.

Many decorative bird boxes are totally unsuitable for parent birds and their families. Bird boxes designed as an integral part of a bird table are unlikely to be occupied due to activity level. Choose a quiet and undisturbed part of your garden for your nest box.

Making a Small-hole nest box

You will need a plank about 15 mm thick. Do not use CCA pressure-treated timber, as the leachates may harm birds.

Cut each section as per diagram. Download nest box diagram.

Use galvenised nails or brass screws to fasten everything together.

Drill a couple of small holes in the base to allow for drainage and keep the nest dry.

It is always best to leave the box untreated. Soft woods will need to be treated with water based preservatives on the outside of the box only. Keep any preservative away from the entrance hole, as birds often tap this regularly with their beak before deciding whether to occupy.

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 would do). Fasten it down with a good catch.

Making a Large-hole nest box

For Starlings and Great Spotted Woodpeckers, use the large box dimensions.

Making an Open-fronted nest box

The small box with 100 mm high open front may attract Robins or Pied Wagtails. A wren would need 140 mm high front panel, while Spotted Flycatchers prefer a low 60 mm front to the box.

Hole sizes

Different size holes are suitable for different types of birds

• 25mm or larger for Blue Tit, Coal Tit and Marsh Tit
• 28mm or larger for Great Tit and Tree Sparrow
• 32mm for House Sparrow and Nuthatch
• 45mm for Starlings

Remember that naturally occuring nest holes don't come in standard sizes, so just use them as a guide.

Access for inspection and cleaning

Nest boxes need an easy access point for inspection and cleaning. Use a waterproof hinge on the roof of the box, so that it can be lifted easily but won’t fall off. Thick rubber hosepipe, car inner tubes or Butyl rubber are ideal waterproof materials to use. Cut the rubber to the width of the box, and then nail or staple the rubber along the back of the box and to the roof to form a hinge.