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Perched, flying away Blue Tits at entrance hole

Hole size for Bluetit box

To force a Blue Tit to nest in your bird box you need to setup one that has a 25mm hole, slightly smaller if possible but any larger will encourage other, larger birds.

Make it a 25mm entrance hole only if you want Blue Tits to nest, well it must also be rounded. With this information, observe the rules for siting a bird box in a shaded area; out of sunlight and westerly winds, with a Tit requiring a box that is 2 to 4 metres high.

Its difficult getting one family of bird species to nest your in your bird box, let alone a single species, so you have a challenge ahead of you.

If Blue Tits are regularly visiting your garden, that's a good start for one thing. If they don't frequent your garden ever, then you may want to forget about it for now.

Bringing a Tit to nest in your box must be close by to where Blue Tits hangout, which is usually when they come to yout bird feeders to eat.

So well you're waiting for a Blue to nest, its quite possible all other types of birds - small or big - may take up the bird box instead.

Well the 25mm entrance hole will likely to attract Blue Tits, follow the rules of siting a bird box by facing it away from the sun and westerly winds at all times.

Its also vital you observe the rules for positioning a multi-use bird box at the height required by Tits; which is 2 to 4 metres for a Blue Tit nesting box.

Furthermore, a Blue Tit will check the quality of the box or alter the edges around the entrance, so a metal plate should not be used.

And that goes for a perch, no box requires a perch near the hole as it would give predators a foothold to take the eggs within.

25mm hole or thereabouts

When setting up a wooden bird box for Blue Tits make it so the entrance hole size is around 25mm, give or take a millimetre.

Well this is the most acceptable hole size to entice a Blue Tit to nest, bare in mind its possible a Tit could nest in a box with a larger or small hole size.

When setting up the box, simply use a ruler or tape measure to measure the hole radius to make sure its a perfect 25mm, then just leave it to nature.

Smallest hole size

Did you know the smallest hole size available on all commercially available bird boxes are drilled to a 25mm radius only.

So therefore, if buying a bird box with this hole size know that its target bird species is a Blue Tit; with the option for a March, Coal or even Great Tit to nest also.

And well it starts small, know that a Tit could alter the hole by making it larger from the outside, as they axe at the hole edge to bring it up to there liking.

Rounded shape only

Entrance hole to a bird box setup for a Tit must always be a 25mm rounded hole only.

Well a suitable hole to bring all types of small garden birds to your nest in your box, its also one that could attract other small birds.

That's with the exception of Robins, Wrens, Woodpeckers or Owls, who all demand a square of rectangular shaped hole - so its not a case of one shape fits all.

Naturally, all other common garden birds will ask for a box that has a entrance that starts anywhere from 28mm up to 32mm.

So just stay within the confines of a small hole just to keep larger birds away for now.

To big will entice other birds

When setting up a bird box to attract Blue Tits only, know that all types of smaller garden birds are going to be interested in nesting, regardless of hole size.

But the biggest problem facing small entrance hole boxes is the possibility of bringing a larger, unwanted bigger bird to nest.

at least among them; House Sparrows, Tree Sparrow or Nuthatch could fit, though this only applies to houses near woodlands in most cases.

And well the box could invite all the Tit family to nest, the Great Tit requires a 28mm hole but will make do with a 25mm if its has to.

Nothing around the hole

Blue Tit perched outside bird box with altered entrance hole
You've setup the bird box in the perfect location; at least 2 to 4 metres of the ground, fixed away from sunlight and isolated in a quiet spot.

Its not perfect though if your have say a perch fixed to the entrance hole.

Know that bird boxes do not need a perch whatsoever, this will only encourage larger birds or predators seeking to steel what's inside.

This also applies to boxes that might of a metal plate fixed to the entrance.

It might be acceptable if you have an issue with predators enlarging the hole to access the interior, but if you don't its absolutely not needed.

For one thing, Blue Tits like to peck around the hole to test it for structure integrity or to chip away the entrance hole edges.

Metal plates won't allow this so would go towards deterring Blue Tits rather then encouraging them to nest.


There you have it, always make sure you setup a wooden bird box with an entrance hole that is no larger than 25mm, or thereabouts.

If its a little smaller this could still bring Tits to nest, as it would also further deter most larger birds if they're thinking aboutusing it, as the hole will be to tight a fit.

Saying that, never use an entrance hole that's larger as it would be made suitable for a whole series of birds, so one might nest before a Blue Tit arrives.

To be successful bringing a Tit to nest in the box, know that you must be already getting regular visitation from Tits in the garden, as its highly unlikely for them to appear from thin air just to nest in your box.

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