How to make a bird box

How do you make your own bird box? And what features should the ideal nest box have? Discover how to build the perfect bird box and where to hang it.

Birds are among our most popular garden visitors because they are both fascinating to watch and delightful to listen to. Many of us put up nest boxes in our gardens to attract birds and give our feathered friends a place to raise their young. Aside from being a fun activity, building your own nest box contributes significantly to bird conversation. It also allows you to watch young birds from the comfort of your own garden. Read on to find out why birds need nest boxes in the first place and what you should bear in mind when building your own.

Why do birds need nest boxes?

People often wonder if and why birds even need nest boxes. After all, do they not build their own nests in nature? Unfortunately, we humans are the reason birds need nest boxes. Many birds nest exclusively in dead trees, suitable wall niches and natural crevices. However, these natural nesting sites are scarce in modern man-made landscapes. Nesting aids provide a suitable alternative for birds to raise their young.

Nest boxes are not only helpful during the breeding season. As birds need to maintain a constant body temperature of 39 to 42 °C, a night without adequate protection against the elements can be fatal. So especially during those cold winter nights, many birds are happy to find some shelter. In fact, some bird species, such as the house sparrow, are known for setting up a winter nest in a nest box. Similarly, insects, squirrels and even bats seek refuge in nest boxes during the colder months.

How to make a bird box: dimensions and suitable materials

There are a few things to consider when building a nest box if you want the inhabitants to really feel at home, starting with the material you use. Suitable materials include wood, terracotta, and even a mix of concrete and wood fibres. The best woods to use for bird boxes include untreated oak, false acacia or larch because they are very weather-resistant. Plywood and chipboard, on the other hand, are unsuitable as they do not withstand moisture or cold well. Avoid using plastic as it is not a permeable material. This means that moisture could collect inside the bird box, causing mould to grow in the nest. Also, plastic is a poor insulator, so the temperatures inside the bird box would fluctuate dramatically.

You can paint or oil your nest box to make it your own, as long as the materials you use are biodegradable and meet the safety requirements for children’s toys. Linseed oil, for example, helps protect wooden bird boxes from dampness and is completely safe for birds. Please keep in mind that bright colours make the nest box more visible to predators. It is best to opt for natural, earthy tones such as greens or browns.

When making a bird box, it is important to pay attention to the correct dimensions. To accommodate the entire brood, the floor of the nest box should be at least 12 × 12 cm. Adding four holes to the bottom of the box, each about five millimetres in diameter, improves airflow and allows the nest to dry faster. Make sure there is a sufficient roof overhang and that the bottom of the entrance hole is at least 17 cm from the bottom of the box. This helps to protect birds from predators trying to steal their eggs.

Important: Do not attach a perch to your homemade bird box as a perch actually aids predators trying to get into the bird box, putting the nesting birds in danger.

What does an ideal bird box look like?

While there are many bird box plans available, the first thing to consider when building a bird box is which bird species will use it. A bird box for tits, for example, has different requirements than one for swifts. Typical rectangular starling or tit bird boxes with round entrance holes are used by numerous cavity-nesting birds. Keep in mind that different bird species have varying preferences when it comes to the size of their entrance holes. As a result, the size of the entrance hole will decide which species is most likely to use your nest box. The table below shows some of the preferred entrance hole sizes for the most common bird species.

Other bird species prefer different shaped nest boxes. In contrast to cavity-nesters, which prefer enclosed nest boxes, open-nesters and birds that rely on nooks and crannies in buildings for nesting are happy with open-fronted nest boxes. Because these boxes are partially open at the front rather than having a small entrance hole, you should place them somewhere hidden from predators. These nest boxes are suitable for robins, spotted flycatchers, white wagtails, and wrens. Swifts are also a little picky about their nesting boxes, preferring vertical boxes (rather than upright ones) with an oval entrance hole (6.4 x 3.2 cm).

How to hang and maintain a nesting box properly

The bird box’s location determines whether or not birds choose to occupy the nest box. Even the best bird box will not be accepted if it is hung in a poor location. As a result, once you have finished building your nest box, it is important to find a suitable location for it.

Keep in mind that the bird box needs to be placed about two to three metres above the ground. The entrance hole should not face the weather (west), nor should it be in full sun or shade. Ideally, hang it somewhere facing east or southeast. Place nest boxes in areas that are protected from the elements, such as a tree, pole, or even a house wall. It is especially important to ensure that open-fronted nest boxes, which birds like robins prefer, are as inaccessible as possible to predators like cats or squirrels.

Once you have found the right spot, hang your homemade bird box with rustproof nails or screws, tilting it forward slightly. For trees, use fixed wire brackets; these do not damage the tree and can be removed gently if necessary. To prevent neighbourly disputes, keep a minimum of ten metres between nesting boxes of the same type. The only exception here is for birds that nest in colonies, such as starlings, swallows, and sparrows. As these birds prefer to stay together in groups, their nest boxes can be hung close together.

If you regularly feed birds in your garden, make sure your nest box is far enough away from the feeding station. Because so many different birds visit them, feeding stations are frequently too crowded for the brood. They also draw the attention of predators, who can then easily locate the nesting site.

Autumn is the best time to put up a bird house. This way, the birds can use it as a winter shelter right away while also having time to build their nest before the breeding season begins. After putting up the nest box, leave it alone because too much commotion will scare the birds away.

Important: Only clean the nest box once a year to remove pests and dirt. It is best to clean it in late summer, once the breeding season is over. Simply remove old nesting material and brush any dirt out of the bird box.

Want to do more for the birds in your garden? Find out how to make your own bird food and which native shrubs are particularly suitable for birds in our in-depth articles. Or to find out how to turn your garden into a real haven for birds, take a look at our article Bird-friendly gardens: Top 10 plants for songbirds.