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Painted wooden bird house in contrast with dark entrance hole

Best size HOLE for birdhouse

Birds who visit our garden to nest in our bird houses do so with a specific hole size in mind - so don't take it for granted as you can encourage or deter certain species.

Best size hole for bird houses would be 32mm; not only can it attract most of the birds that use houses, but it is possible to see Tits who would prefer a smaller hole size. To attract smaller common garden birds only then, a 25mm entrance hole will do, but you can alter the hole size with an entrance hole plate.

Setting up a wooden bird house in our gardens by using a certain hole size is not for show - it serves to attract certain species to make a home in our bird houses.

It can indeed be difficult to attract birds to nest in our garden so its therefore imperative you attract as many bird species as possible.

I then recommend use of a 32mm size hole for this purpose, as a hole size too small or large can only cater to a lower number.

But if its small common garden birds you only hope to nest, then use of a bird house that has a 25mm entrance hole size.

Entrance hole size exceeding 32mm attracts less birds, but then in turn can attract fewer smaller birds - as the hole size is far too big for their needs.

It may be possible you are in ownership of a bird house you bought recently, but don't worry as a cheap to buy entrance hole plate can change the hole size to your liking.

What birds use bird houses can include up to twenty-two species, but this number is drastically shorten when you exclude the birds who only nest in wooded areas with a garden in a very specific location.

It could be then you can only seriously attract as few as 7 or 8 wild bird species.

Recommended size hole table

Bird Species: Hole Size:
Barn Owl 120mm
Blackbird 130mm
Blue Tit 25mm
Coal Tit 25mm
Great Tit 28mm
House Martin 45mm
House Sparrow 28mm
Jackdaw 120mm x 120mm
Kestrel 120mm
Marsh Tits 25mm
Nuthatch 32mm
Pied Flycatchers 28mm
Pied Wagtail 100mm high
Robin 100mm high
Starling 45mm
Spotted Flycatcher 60mm high
Stock Doves 120mm
Swifts 28mm x 65mm
Tawny Owl 270mm - 230mm
Tree Sparrow 28mm
Woodpecker 45mm
Wren 140mm

32mm will attract MOST birds

While the smallest common garden birds prefer a bird house entrance hole of 25mm, the medium size garden birds are suited to a 32mm size hole.

However, that is not a definite because as you may find out, you can indeed attract birds who use a certain hole size - to only then nest in one that is far bigger or smaller.

I can confirm then the best size hole for bird houses would be a standard 32mm.

Now what that means is the Tits, Sparrows and Nuthatches are the suitors to bird houses using an entrance hole of this size.

Great then because its mostly these birds that you'd see more nest in your bird house.

Perhaps with the exception of House Sparrows who prefer a terrace bird house, so a single hole bird house might deter them rather than attract them.

Make it a bird house for medium to small size wild birds than by using a 32mm hole size only. It can bring in as many different bird species as possible - with those who are happy to nest in this hole size.

25mm limit to SMALL birds

If you intend to setup a bird house in your garden with the intention of only attracting small garden birds to it only, then its possible to deter medium to larger size birds.

Do know though medium size birds who prefer a 32mm hole size for bird houses can and will nest in one using a smaller hole.

However, to use a bird house with a 25mm entrance hole can certainly do its best in bringing much of the Tit family to nest in it only.

You can then expect to see Blue Tits, Coal Tits and Marsh Tits nest in 25mm bird house, whereas a Great Tit or Pied Flycatcher prefer a 28mm hole size, but you could still see them use your 25mm entrance hole.

Its therefore safe to say this smaller bird house entrance hole setting is going to attract the most garden birds as possible, in the small size only.

I don't recommend using this setting to guarantee nesting birds though; for that I would prefer a bird house using a 32mm hole as all birds mentioned can still nest in this size.

45mm LARGE birds only

While limited to the largest common garden birds only, a 45mm bird house hole size should be considered if its only larger birds you wish to attract.

Understand though a hole size of 45mm is often overlooked as smaller birds know it can be too much trouble for them - as it can attract predators to steel or kill their young while still in the bird house.

Rather than attracting a whole host of garden birds then, its only that of Great Spotted Woodpecker and Starling who could truly nest in this hole size bird house.

Trouble is woodpeckers are restricted to gardens near wooded areas, whereas starlings generally are more difficult to attract over more common garden visitors.

Not many birds who regularly use smaller bird house entrance holes below 32mm then will take up residence - I therefore recommend only using this hole setting if you can guarantee woodpeckers or starlings showing interest.

Entrance plate to adjust hole size

Its quite possible you've already invested in a bird house that you may now believe to be no good, after taking onboard my recommended hole size for bird houses should be.

Don't despair as there's certainly a way to quickly correct the error.

If using a bird house that is uses an entrance hole size above 32mm, then its possible to use a bird house entrance hole plate of 32mm - therefore it quickly becomes a bird house with a hole size of 32mm only.

And don't worry, an altered or changed hole size using a metal plate is not going to turn many of them away.

However, only using a 32mm metal plate on an original hole size larger makes sense, but you can customise your bird house entrance hole of 32mm to a size smaller if you intend to attract smaller birds.

Make it an entrance hole size of 25mm then as to limit what bird species can nest.

Robins or Wren open front

Common garden bird that hasn't been mentioned thus far is of course the Robin, but you must know Robins don't use bird houses in the traditional sense.

To buy a Robin bird house it must be a specialty one that uses an open front, which happens to a suitor to Wrens - but are seen less at the bird house.

I don't recommend using a Robin bird house as you can only attract them or few other species to nest. So to be the best size hole for bird houses it won't be a house design that requires a large open front.

But you shouldn't neglect the possibility of bringing Robins into your garden to nest, so if the garden landscape allows it, you could still setup a Robin box - if it can be set back into overgrowth, up to two metres off the ground.

This would of course be setup far away from any second or third bird house setup, so do make sure they are far apart.

Best hole size summary

To be the best size hole for a bird house I would absolutely recommend a bird house that uses a 32mm rounded hole setting.

Its therefore possible to attract as many wild bird species as possible, all of whom would be willing to use an entrance hole of this size.

Generally, most Tits prefer a hole size of 25mm, but to be 32mm you can still encourage them to use it - all the way up to Nuthatches you use this hole size specifically.

Bird houses that use a 32mm hole size can attract all nesting Tits, Sparrows - with exception of a terrace box in use - while attracting Pied Flycatchers also a possibility.

However, you may want to attract the smallest common garden birds only, so I would then recommend use of a bird house with a 25mm entrance hole only.

Once again its still possible to see birds who don't often use this small hole size bird house to still use it - but it certainly can help you to restrict nesting to small to medium size birds.

If you want to attract a small number of large birds, then make it a bird house with a 45mm hole size - but it is limited as smaller birds don't setup a home in a bird house using such a large hole.

You can still change your bird house entrance hole size by using an entrance hole metal plate - with sizes 25mm to 32mm as standard available to buy.

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