Siting a Nest Box: Why Position Beats Design Every Time
A nest box succeeds or fails on where it is hung far more often than on how it is built. The British Trust for Ornithology’s nest record scheme has long shown that occupancy rates swing sharply with orientation, height and surrounding cover, even when the boxes themselves are identical. Get the mounting right and an ordinary box will be used season after season; get it wrong and even a beautifully jointed one will sit empty.
North to east, and the 30-degree rule
Holes should face between north and east, so the box avoids the strongest sun and the prevailing south-westerly rain. A box facing due south can overheat in a warm May, and overheating is a documented cause of chick mortality in small tit species. A box fixed to a north-facing shed wall in a Shropshire garden, for example, will stay cooler through the critical first three weeks after hatching than an identical one on the same plot’s south wall. The takeaway is simple: check a compass before you drill, and treat full afternoon sun as a fault to be corrected.
Height is a compromise, not a preference
Two to four metres is the working range for blue tits and great tits. Lower boxes are easier for cats to reach; higher ones are harder to inspect and clean, and small birds generally avoid exposed positions above the canopy. A wildzy box mounted at roughly 2.5 metres on a clear section of trunk sits in the sweet spot for both maintenance and predation risk. Choose the height you can still reach safely from a stepladder, then work the rest of the placement around that practical limit.
Hole size decides the tenant
The entrance diameter effectively pre-selects the species, so match it deliberately: 25 mm for blue tits and coal tits, 32 mm for great tits and tree sparrows, 45 mm for starlings and house sparrows. A 25 mm box on a plot with a healthy great tit population will simply be ignored until a smaller bird finds it. Position the hole at least 15 cm above the floor to leave room for the nest cup and to keep developing chicks away from the entrance where predators can reach them.
Predators and the clear flight zone
Predation pressure is the single biggest cause of nest failure, and most of it is preventable through placement. A metal plate around the entrance stops squirrels and woodpeckers enlarging the hole; removing nearby climbing routes — dense shrubs, fence posts, leaning branches — keeps cats from reaching the box. Keep feeders at least three or four metres away, because the constant traffic of feeding birds draws attention to the box. The takeaway: think like a predator for five minutes before you fix the bracket.
Cleaning and the autumn window
Old nests should come out once breeding has finished, ideally between September and November. A nest left in place harbours fleas, mites and mould through the winter, and the next pair will spend days clearing it out. Scrape the box empty, scrub it with boiling water rather than chemical disinfectants, and let it dry fully before rehanging. Untreated timber of at least 19 mm thickness insulates well and breathes; the drainage holes in the base and the small ventilation gaps near the top are what keep the interior dry. A wildzy box cleaned on that schedule will typically outlast several cheaper alternatives that crack, warp or trap condensation.