Nest Boxes – our experience

10th March 2022

by Ines Kisielewski, Partnerships Executive

We now have three years data from the 27 nest boxes we placed in our ancient woodlands at Bank Woods, ready for the nesting season of 2019. So we thought it might be useful to share what we have learnt, along with some facts from experts such as the RSPB.

Below are some suggestions if you would like to build a nest box, and the results we achieved in our own nest boxes. You can sponsor one of our nest boxes here.

Size and Construction

The construction and positioning of a birdhouse will not only determine whether it is an effective shelter for its desired residents, but also what types of visitors it will be receiving. The size of a nesting box is not standardised as each different species of bird will require different dimensions.

Recommended types of wood:

  • Any kind of thick weatherproof timber.
  • No CCA pressure-treated timber as it may harm the birds.
  • You can use water-based preservatives on the wood such as Sadolin which are safe for animals.
  • Woodpecker boxes can be filled with balsa wood, rotting log or wood chips as they like to excavate their own nesting cavities.
  • If your box is exposed to rain it can be covered by recycled leather or rubber which may prolong its life.

The entrance:

The entrance hole needs to be at least 12.5cm from the floor of the nestbox so as to avoid young birds falling out or predators (including pet cats) scooping them out.

The size of the entrance hole depends on what species of bird you are hoping to attract. These are guidelines for various species of bird:

  • 25 mm – blue, coal and marsh tits
  • 28 mm – great tits, tree sparrows and pied flycatchers
  • 32 mm – house sparrows and nuthatches
  • 45 mm – starlings
  • Open fronted box – robins and wrens

Your main focus should be on whether the nestbox is secure, weather proof and sheltered from predators rather than the precision of the dimensions.


In our ancient woodland, we have 27 boxes spread out over approximately 20 acres. We were advised to position them in groups of three. The idea was that early in the season, blue tits and great tits would occupy one each of the trio. As these birds are territorial, the third box would remain unoccupied – and would be the perfect nesting spot for summer migrant birds who would arrive later. If placing your box in a garden situation, this may not be a consideration. Here are some things to think about:

Siting the box:

  • In order to protect the birds from extreme weather (strong winds or sunlight), the box should generally face between North and East.  
  • For tits, sparrows, woodpeckers and starlings: the box should be fixed 2-4 metres high and with a clear flight-path
  • For robins and wrens: Need to be open-fronted and below 2 metres high
  • Avoid placing the box near a bird-table or feeding area as this may deter birds from breeding nearby

Attaching the box to a tree or wall:

  • You should tilt the box forward slightly in order for rain to drip down the sides.
  • If attaching to a tree, to avoid damage, you can use wire with a piece of a tyre or a hose around it, wrapped round the tree, rather than nails.
  • The best time to set up a bird box is during autumn and winter. It may then be used for roosting and feeding, and then for nesting the following spring.
Putting up a nest box



  • We have been taught how to check our boxes without disturbing the occupants. We wouldn’t recommend checking your nest boxes, unless you have been shown how to do this safely.


  • The boxes should be emptied and cleaned once a year at the end of each breeding season around October.
  • In order to properly clean your bird box it is best to take it down and dip it in boiling water in order to kill any parasites.
  • It is best to avoid any insecticides or flea-powders which may be toxic to birds … and boiling water is a lot cheaper!
  • It is illegal to keep unhatched eggs and they should be removed.


There are many potential predators, including cats, squirrels, rats, mice, stoats, weasels and larger species of birds such as woodpeckers or crows. These predators tend to hunt in the early hours of the mornings and we are therefore often unaware of their presence

Unusual occupants

We have had bees, wasps and bats making their homes in our nest boxes!

Pipistrelle bat in a bird box

Our Bird boxes

We put up our 27 birdboxes in our various ancient woodlands at Bank Woods in late summer of 2018. We check them and clean them out every year.

Our bird boxes have a 32mm hole in order to allow for a large range of species. We based our design on the RSPB’s instructions. We made them from tantalised timber, and used screws rather than nails in the construction, to make the boxes stronger.  We use metal plates to protect the edges of the entrance holes, to protect them from squirrel and woodpecker damage. We have a cunning adaptation to the way the lids close, to allow easy access for checking and cleaning out the boxes. They are secured with a thick wire which is wound round a screw on each side.


When checked in 2019, 19 boxes had been used for nesting. There were 17 broods of tits, either blue tits or great tits, and 2 pied flycatcher nests. We were pleased with this 70% occupancy of the boxes in their first season.

In the 2020 season, only three nest boxes remained unoccupied, meaning an occupancy rate of 89%. Four were occupied by pied flycatchers, one by a nuthatch, and the rest great and blue tits.

85% of the boxes were occupied in 2021, we had four pied fly catchers, two nuthatches and 17 tit nests.

Blue tit and great tit nests and eggs are hard to tell apart, but once the chicks have feathers, it gets a bit easier. Both species make nests of moss and feathers, and they lay tiny cream speckled eggs, deep in a cup in the nest. Pied flycatcher nests are quite different, made of dry stems and leaves, and their eggs are blue. As later arrivals, having migrated from Africa, pied flycatcher broods are always less advanced than tit broods at the time of checking.

We have looked at the species of birds occupying the nest boxes in each ‘trio’. We only have three examples across three years of data, where all three were occupied by tits. Generally, the third box will remain empty, or will be occupied by a pied flycatcher or nut hatch.

Looking at the occupancy longitudinally, in 2021, three of the pied flycatchers made their nests in boxes previously occupied by other pied fly catchers.  We wonder if the same birds returned? Or were these offspring of earlier roosts? One of our boxes was occupied by pied flycatchers every year.

Only one individual box has remained unoccupied every year. In the three years we have had our bird boxes, they have helped 64 broods of birds into the world!


Birdboxes are a great way to help support our wildlife. They are cheap and easy to make, and offer useful replacement nesting sites for birds whose existing homes have been lost through development. At Make it Wild, we believe in our supporting our wildlife as best we can. Hopefully our results have encouraged you to build and put up your very own birdboxes at home!

You can sponsor one of our nest boxes here.