Blue tit at a nestbox © James Gallagher
SMALL BOXES WITH HOLES
To attract blue and great tits, the BTO advises placing your nestbox between 1m and 5m above the ground. However, coal tits prefer a box no more than 1m high. A house sparrow will look for a box at least 2m high, whereas a nuthatch prefers a box at least 3m high. Make sure that foliage is not obscuring the entrance hole so that birds have a clear view outside and can avoid predators.
25mm hole Coal tit, blue tit, marsh tit
28mm hole Great tit
32mm hole House sparrow, nuthatch
SMALL OPEN-FRONTED BOXES
Birds that use small open-fronted boxes are prone to predation when they’re sitting on eggs. So put the box high enough to deter cats, and ensure that thick vegetation is growing across the front of the box for additional protection. The standard design uses the 100mm front panel.
60mm high at front Spotted flycatcher
100mm high at front Robin, pied wagtail
140mm at front Wren
MEDIUM BOXES WITH HOLES
These boxes are designed to attract starlings and great spotted woodpeckers, which favour sites over 2.5m high and over 3m high respectively. In areas where there are fewer alternative nest sites, such as dead trees and pan-tile or corrugated roofs, these boxes can be more successful at attracting starlings.
Oval-shaped hole Swift
45mm hole Starling
50mm hole Great spotted woodpecker
NESTING IN COLONIES
House sparrows, house martins, swifts and starlings prefer to nest in loose colonies high up in the eaves. Space out two or three nestboxes on the same side of your house.
NATURAL NEST SITES
Many garden birds will nest inside hollow trunks or cavities in rotten branches, but others prefer to make their own nest among dense foliage. Plants such as holly, whitebeam, hawthorn, blackthorn, firethorn and cotoneaster offer great natural cover – avoid trimming branches until pairs have finished nesting. Climbers such as Virginia creeper, honeysuckle, ivy and clematis also provide ideal nest sites.
A nestbox should be constructed from an insulating material, such as durable cedar, oak or beechwood – don’t choose one that is made from plastic, ceramic or corrosive materials.
The wood of the nestbox should ideally be 19mm thick (no less than 15mm) and the internal floor area should be at least 130cm² to give parent birds enough room to incubate their eggs and brood the young. Remember too that the diameter of the nestbox hole should be suitable for the type of species you hope to attract.
A good nestbox should be accessible and not too high so you can clean it out easily. Wooden boxes can be treated on the outside with a preservative provided that it is non-toxic and water-based.
Find out more about the BTO’s National Nest Box Week.