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Unused Blackbird nest box mounted to tree trunk

Blackbird nest box hole size

Setup up a bird box specifically to attract Blackbirds to it, but remember such a box can bring Robins, Wrens or Spotted Flycatchers.

Make use of specialty Blackbird nest box that uses a hole size width of approximately 200-300mm, with a safe 100mm height. Hole size width would normally be the width of the box itself, but must retain its 100mm high hole size. Entrance hole on Blackbird nest boxes would normally continue on each side.

Blackbirds visiting your garden all year round just maybe willing to nest in your bird box if you site the box in the correct position.

Its vital then to bury the Blackbird nest box deep into shrubs, ivy or a hedgerow up to 1-2m off the ground - where you site a bird box for a Blackbird is just as important when buying or building a box with a correct entrance hole size.

To be a hole size of 200mm by 100mm would be a smaller than normal box, whereas Blackbirds thrive on a larger entrance hole size, so you could see more success.

Make it so it uses a whopping 300mm wide entrance with the standard 100mm height.

Nothing then can stop Blackbirds nesting in your bird box, providing its setup in the best possible location.

No best size hole for a bird box that will accommodate a Blackbird, as they are only an approximate - so to give or take a few centimetres would be within a margin or error.

200-300mm width

Medium size garden birds can't make do with a regular bird box for small birds, so would need a larger box to accommodate its size.

Its therefore possible to build or buy a nest box for Blackbirds with a width of 200mm or less - but up to a whopping 300mm is within reason.

To be 180-220mm would be classed as a small bird box, but this entrance hole opening can either attract or deter Blackbirds from nesting.

Smaller sizes would be fitting to a bird box for use by Robins or Wrens, whereas the larger, recommended size would only attract Blackbirds.

The 200-300mm entrance hole size width is not so much cut into the front, but more so is the entire width of the box - right up to either side.

100mm height hole size

Now that you know a 200-300 hole size is a requirement for a Blackbird nest box, what about the height of this entrance hole.

Again, a medium size common garden bird so would need a decent height as to not be too restricted for entering and exiting the box.

I can guarantee a 100mm nest box entrance hole size height would be all you need.

This again can vary but its more likely to be larger than smaller in size, but as a rule - if a Blackbird can perch on this open front with space above it, then its a good fit.

Make it 100mm only and you'd be in good hands with no restrictions or no possible way of deterring potential Blackbird nesters.

Open fronted design

Blackbird nest box hole size would therefore be 200-300mm wide by 100mm high, or with a 20-30cm width or 10cm tall entrance.

Much like the Robin, Wren or Spotted Flycatcher, the Blackbird requires quite a large open fronted bird box.

Blackbirds are unlikely to nest in a standard bird box designed for small garden birds, in which are made with a rounded entrance hole shape.

And on top of that, the entrance hole for a Blackbird would be larger than that belonging to a Robin or Wren, with a Blackbird nest box size being much larger overall.

Square shaped bird boxes for Blackbirds would see an entrance hole in a narrower shape, but an entrance hole with the 100mm height intact. Whereas much wider Blackbird bird boxes would see this 100mm tall entrance appear as a postbox slot.

Side openings optional

What is unique to the Blackbird nest box over say a similar yet smaller box for a Robin, Wren or Spotted Flycatcher - is the distinctive side openings.

What that refers to, the 200-300mm by 100mm entrance hole appears to have gaps on either side, which Blackbirds like - this entrance hole would then carry on around the sides of the bird box.

You'd then see what is a letterbox shaped entrance hole on the front of the box, but it then carries on up to 4-5cm on each side.

Not always mind you in the smaller boxes, but for larger boxes or those seen with a 300mm wide entrance hole - expect the hole to be seen on the side, joined up to the front hole.

That is due to the way how Blackbirds build their nests in nature, so it sort of mimics this natural nest so must be quite open to the elements.

Medium size bird nest box

If you are building a nest box for a Blackbird then remember this is not a small common garden bird, but one that is larger than most.

Its imperative then to build this bird box to accommodate its size.

To do this you must remember the average measurements of a Blackbird to be 24-25cm in length, with a 34-38.5cm wingspan - so far larger than say a Tit or House Sparrow.

To build a nest box while taking into consideration these measurements, you won't go wrong.

In buying a Blackbird nest box, all these statistics are taking into consideration, with how big or small a Blackbird nest box should be, common knowledge already .

As well as the male and female Blackbirds, space is needed for up to five eggs, so these large boxes to accommodate this medium size bird are within the scope needed.

Hole size attracts others

To setup a bird box specifically to attract Blackbirds can be so if you site it in the correct location, but there could be an issue ahead.

Blackbird bird boxes are actually like those made for Robins, Wren or Spotted Flycatchers, its therefore possible any one of these garden bird species may take up residence first.

What is more awkward is where you put a Robin bird box or one for a Wren, is where you'd site a nest box for a Blackbird. Expect then to see either species move into your box that was intended for Blackbirds only.

There is a silver lining though, to give you a better chance of seeing Blackbirds only move in - you could use the largest available box size.

Robins and especially the Wren are Britains smallest garden birds; to use a too large box could deter them from using it, as its far too big for too small birds.

Blackbird nest box size summary

No one size fits all entrance hole for Blackbirds, but there's certainly a size your can shoot for to at least stand a chance of seeing Blackbirds nest in your box.

But first, remember this is going to be an open fronted nest box so can accommodate other, smaller common garden birds who use this hole size bird box; can include Robins, Wrens or Spotted Flycatchers who may move in.

However, to make it a larger wooden bird box for Blackbirds could deter the small garden birds.

Its vital you maintain a 100mm - or 10cm - high entrance hole size regardless of size of the box - along with a 200-300mm wide hole.

The 300mm width relates to the largest boxes you can buy or you should make, with the 200mm recommendation used on smaller, less successful boxes for Blackbirds.

Blackbird boxes must always use an open front or else they won't move in, but its certainly possible the entrance hole can continue on either side of the box.

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