THE SITE
High, north-east, no feeder
Place it facing north-east, away from sun traps and the prevailing wind and rain. BTO suggests 2 to 3 metres up for blue tits and house sparrows, and not near a bird table.
Pick a hole sizeA NEST BOX, BUILT RIGHT
Build it,
then leave it be.
A plank, a saw and the right size hole.
25 MM for blue tits
12 cm Minimum height of the hole above the floor
- Thick wood, no perch
- Face it north-east
- Clean Sep to Jan
- Small details, more chicks
Old trees, loose roof tiles and gaps in barge boards are disappearing, and cavity-nesting birds have lost out. The British Trust for Ornithology says a well-made nest box can replace those lost sites, if the details are right.
THE SHORT ANSWER
Get the box right,
then stay away.
Most of what matters is decided at the workbench.
After that, the law asks you to keep your distance.
THE BUILD
Walls at least 15 mm
BTO advises wood at least 15 mm thick, drainage holes in the floor, a roof that lifts for cleaning, and no perch on the front, which only helps predators.
Build steps
THE LAW
Hands off while in use
In England it is an offence to intentionally take, damage or destroy a wild bird's nest while it is being used or built. Wait until nesting has finished.
See the numbersWHICH BIRD, WHICH BOX?
Pick a bird,
size the opening.
Choose a garden bird to see the entrance it needs. The bar shows how big the opening is, from a small 25 mm hole to an open front.
From BTO's nest box guide and the Natural History Museum's bird box advice.
FOUR STEPS FROM PLANK TO BOX
One plank,
one season ahead.
BTO's small hole-fronted box uses a single plank of about 150 by 1170 mm. These are the steps and checks its guide stresses.
Choose the wood
Pine is easy to cut and its resins help it last. Use wood at least 15 mm thick, with screws or nails and glue for strength.
Drill the holes
Cut the entrance to the size your bird needs, drill small drainage holes in the base and pre-drill the back plate for fixing.
Treat only the outside
Use a water-based preservative on the outside and leave the inside bare. There is no need to add any lining or nesting material.
Put it up early
Some birds look for sites before National Nest Box Week in mid-February, so fix the box as early in the year as you can.
TWO NUMBERS WORTH KNOWING
Why the details
matter to a chick.
One measurement that keeps predators out,
one figure for what a single box can hold.
12 cm
Minimum height of the hole above the floor
BTO says the hole should be at least 12 cm above the floor of the box to stop predators reaching in, with an inside cavity at least 15 cm across.
BOX DESIGN · BTO
8–10 eggs
Typical blue tit clutch
Blue tits raise one brood a year, mostly laid in April and May. Incubation takes about 12 days and chicks fledge at 16 to 22 days.
BLUE TIT · BTO NEST RECORDS
BTO notes that boxes made from thin wood, plastic, metal or solid ceramic may overheat, which is dangerous for birds. It recommends waterproof, insulating material such as wood or woodcrete.
CLEANING OUT
Clean it once,
in the right months.
BTO advises cleaning boxes out every year between 1 September and 31 January, checking first, as some birds breed early or late. Removing old nests may cut the fleas and other parasites waiting for next season.
The Natural History Museum suggests boiling water and a scrub rather than household cleaners, which may be toxic to wildlife, and gloves and a dust mask for you. Unhatched eggs left behind may not be kept or sold.
Questions
Questions people ask
What size hole should a nest box have?
BTO and the Natural History Museum give 25 mm for blue tits and coal tits, 28 mm for great tits, and 32 mm for house sparrows and nuthatches. Robins prefer an open-fronted box.
Which way should a nest box face?
North-east is the usual advice. In the UK wind and rain mostly come from the south-west, and a south-facing wall can turn a box into a sun trap.
Should a nest box have a perch?
No. BTO says nesting birds do not need one and a perch makes it easier for predators to get in.
Can I move or clean a box with a nest in it?
Not while it is in use. In England it is an offence to intentionally take, damage or destroy a wild bird's nest while it is being used or built. BTO suggests cleaning between 1 September and 31 January, after checking it is empty.
Nobody moved in. What now?
Give it time. The Natural History Museum suggests leaving a box up for a few years, and moving it if it is still empty after three.
Where the facts come from
Updated