When siting your box, consideration must always be given to ensure that it is not accessible to predators. In gardens, the most likely predators will be cats and grey squirrels. Unfortunately, it is often very difficult to prevent determined squirrels from reaching your nest box. An unprotected entrance hole is then very open to attack from a squirrel, which will gnaw away at the wood until the hole is wide enough for it to gain access to the contents, be they eggs or nestlings. However, a further measure you can take to stop them doing this is to fit a metal plate over the entrance hole. These plates are available commercially and can be purchased from any good garden centre or bird care company at very little cost. A nest box should never be sited close to a bird table or bird feeders, as large numbers of feeding birds will disturb potential nesting pairs. It is best to fix small-hole boxes, for species such as Blue Tit and Great Tit, on to tree trunks 1-3m above the ground, but avoid sites where foliage obscures the entrance hole. In gardens without trees then fitting them to the side of a shed or a wall is the next best option. The front of the box should be angled vertically or slightly downwards so that rain cannot enter through the hole.

Erecting the box

When putting your nest box up, remember to use galvanised/stainless steel screws or nails as these will not rust. If fixing boxes to trees, galvanised wire can be used to tie the box to the trunk or hang it from a branch. All fixings should be inspected regularly to ensure the box remains securely attached.

Traditionally, nest boxes for small birds are put up in the spring. Pairs begin to prospect in the latter half of February, so a box put up now stands a good chance of attracting nesting birds. However, it is never too early to put up a nest box, as some birds will use them to roost in during the winter months.

Unused boxes

While we can increase the probability of a box being used by choosing a suitable location, there are lots of factors that we don’t know about, such as the number of pairs of birds in the area, the presence of natural nest cavities nearby and the location of territory boundaries. While some boxes may be taken up immediately, others may remain vacant, often for no apparent reason. If a box is not used for several years in succession it may be worth resiting it.

Species such as Robin and Spotted Flycatcher, which nest in open-fronted nest boxes, prefer sites that are hidden from view, so attach your box to a wall or fence that has shrubs and creepers growing against it. The height of the box is less important than the amount of cover - Robins can nest close to the ground or high in ivy.

For other types of nest boxes and further information, see the BTO Nestbox Guide, available as an online purchase by clicking here.