Nest boxes: siting, cleaning, and monitoring

Why a good box in the wrong place fails

A nest box is only ever as good as its position. You can build the finest timber box in the county, but if it hangs in full afternoon sun on a south-facing wall it will cook. If it sits within easy reach of a cat it becomes a feeding station. Getting the siting right takes ten minutes and makes the difference between a box that is used for years and one that never sees a clutch of eggs.

Over the years I have learned that birds are fussy about three things above all: temperature, shelter and safety. Sort those out and the rest tends to follow.

Face the box between north and east

The single most useful rule is to point the entrance hole somewhere between north and east. This keeps the box out of the strongest midday and afternoon sunshine, and away from the prevailing south-westerly wind and rain that sweeps across most of Britain. A little early morning sun is welcome, warming the box gently after a cold night, but baking heat is not.

If your only option is a west or south-facing wall, choose a spot that falls into shade by early afternoon, perhaps under the dappled cover of a deciduous tree. A slight forward tilt of a few degrees helps rain run off the roof rather than into the entrance. Tilt too far and eggs can roll towards the hole.

Keep the space directly in front of the entrance clear of dense foliage. Birds want a clear flight path and a perch nearby to check that the coast is clear before entering.

Height, fixing and keeping predators out

Most garden birds are happy with a box between 2 and 4 metres up. Small boxes for blue tits and coal tits can go a little lower, around 2 metres, while boxes for house sparrows and starlings do well higher. What matters more than exact height is that the box is difficult to reach from below.

• Mount boxes on a smooth pole with a baffle, or on a wall with no climbing frame nearby.
• Avoid placing them just below a branch that a cat or grey squirrel can drop from.
• Fit a metal plate around the entrance hole to stop squirrels and woodpeckers enlarging it.
• Angle the box slightly forward so rain runs off, but not so much that the contents shift.
• Use galvanised screws or a bracket that will not rust, and check the fixings each spring.

Do not put a perch below the hole. Perches were once standard, but they give predators a handy foothold and are of no real use to the birds themselves.

Cleaning: wait for the last bird to fledge

Under UK law you must not disturb a nest that is in use. That means no cleaning while eggs or chicks are present, and no opening the box just to peek. Wait until you are certain the brood has fledged. Most garden species finish by late summer, though some pairs raise a second brood, so leave the box alone until at least late August and often into September or October.

When you do clean, work methodically:

• Wear gloves and open the box carefully, ideally in dry weather.
• Remove the old nest material and bag it for the bin, not the compost heap, where parasites can linger.
• Check the corners and joints for fleas, mites, lice and blowfly larvae. These hitch a ride on old nests and can weaken next year's chicks.
• Scrub the inside with hot water and a stiff brush. Avoid detergents and chemicals.
• Let the box dry thoroughly before closing it up, and do not add new nesting material. Birds prefer to build their own.

If you find a wasp nest or a family of hibernating mice, leave it until spring, then clean once it is empty.

Monitoring without causing harm

Recording what happens in your boxes turns a pleasant hobby into genuinely useful citizen science. Note the date you first see nesting material, the date the first egg appears, the clutch size, the hatching date and the number of chicks that fledge. A small notebook or a spreadsheet is enough; you do not need any special equipment.

Keep visits brief and infrequent. Check once when you expect incubation to be finished and once more shortly before the chicks fledge. Avoid early mornings and cold, wet days, when the adults most need to be on the nest. Never open a box if you can hear chicks that sound close to leaving, as you risk pushing them out early.

Over the years your records will reveal patterns: which boxes are chosen, which years are good, and which species are struggling. That is exactly the kind of detail that helps British bird conservation, and it comes free with a box on the wall.