Filling your garden with holes

This February, the RSPB’s Wildlife Gardener Adrian Thomas reflects on nesting season and the use of different sized nestboxes by different species of bird. Read on to discover which birds are eyeing up his nestboxes!

A person installing a nestbox in a courtyard.
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For most of the winter, no Starling ventures anywhere near my garden. They flock onto the local park where they poke enthusiastically in the short turf, but my leafy garden isn’t their preferred haunt. 

But with spring almost upon us, a male has once again taken up his position in the bare Horse Chestnut tree in the street outside, where he sings and sings his strange song full of clicks and bleeps and wolf-whistles. 

His perch is in direct view of the Starling nestbox on the front of my house. I assume it is the same male as last year, but it could be one of the ‘kids’ of 2023 come back to stake his claim, or a brand-new male. But the fact remains – my nestbox is what draws them here. 

A Starling box and bat box installed on a house, just below the roof.

Holes make homes

Attracting hole-nesting birds to breed in your garden or outside space is one of the delights of wildlife-friendly gardening. The basic idea is of course quite simple – in ancient woodland, birds that like to nest in holes have access to all sorts of natural rot holes (and old woodpecker holes) in old trees. In contrast, gardens are generally too young to have such opportunities, so we can mimic these natural sites by providing artificial holes. 

There used to be another surfeit of holes that birds took advantage of. In the past, our houses were peppered with gaps that birds could squeeze into: under the eaves, beneath roof tiles, even in thatch. House Sparrows, Starlings and Swifts were especially fond of such places. 

Today, people are very adept at filling up any such holes, and new-builds usually don’t have any opportunities whatsoever. Once again, it is easy to provide those birds with a replacement. 

A House Sparrow flying out of a Great Tit nestbox, attached to a tree.

One size does not fit all!

I’m often asked whether it is ok to put up more than one nestbox and my answer is a categorical ‘yes’! Firstly, different species need different types of box. A Blue Tit needs a 26mm diameter round hole, a Great Tit 29mm, a House Sparrow 32mm, and a Starling 45mm. Robins need an open-fronted box tucked away behind thick climbers or bushes. House Martins need artificial cups under the eaves. And Swifts need special bricks or boxes under the eaves with a clear flight line in. You could put up a box for each of them! 

A person stood on a ladder, installing three nestboxes on a brick wall.

Build your community of hole-nesters

Also, some hole-nesting birds, such as House Sparrows, Starlings, Swifts and House Martins, are semi-colonial, and if you put up several in fairly close proximity, you may actually increase your chances of success. 

My totals are now:

  • Five House Sparrow boxes  
  • Three Starling boxes  
  • One Swift box  
  • Two House Martin cups  
  • Five bat boxes  
  • Six tit boxes  
  • Three Stock Dove boxes  
  • Three Wren/Robin boxes  
  • One Tawny Owl box
A large wooden Tawny Owl nestbox installed on a tree.

Not all of these boxes have been used, and not all of them will be used by the species for which they were intended. Indeed, a Wood Pigeon once nested in a Kestrel box, Stock Doves nest in my Tawny Owl box, and another pair of Starlings nests in my Swift box. But that’s fine! 

If you'd like to boost your invitation to new tenants, then we’ve got everything you need at the RSPB shop. So, go on, turn your house and garden into a thriving nursery, the talk of the town for a whole new community of hole-nesters! 

A wooden nest box with a green 'A' shaped roof and a small circular entrance
Apex Starling nestbox - available at the RSPB Shop
Welcome the birds with a nestbox
Find everything you need at the RSPB shop.