Before you start (cont.)

What are the long-term implications of putting up a nestbox?

Providing a nesting site for quite a large bird like the Tawny Owl isn't the same as putting up a box for small birds. Tawny nestboxes are big and quite heavy, so they and the attachment to the tree have to be checked from time to time. There is at least one report on the internet of an owl family being killed when a nestbox fell to the ground. On top of that, owl chicks are messy and nestboxes are best cleaned out every year. So, it's advisable to check every year that the attachment to the tree is secure (with binos or by climbing up) and to take the box down every 2-3 years to clean thoroughly and do any necessary repairs and weather-proofing. This is best done soon after the chicks have left, and the box should be back up by early September. When not in use squirrels are likely to make dreys in the box, and the resulting thick mass of leaves and twigs must be removed -- owls can't do this.

Finally, you're taking on a duty of care to a pair of owls! The likelihood is that by providing them with a safe site to rear young you're greatly enhancing their chances of reproductive success. This is because so many tawnies now have to use the open nests of other species, which are not safe for the chicks. To some extent, therefore, they become dependent on you. So consider what happens if, for example, you sell up and are no longer able to maintain the nestbox. Unfortunately, unlike boxes for smaller species an owl box should not be left up if there is no guarantee that the next owner will maintain it properly.

Squirrels find nestboxes attractive too, and as the owls can't do it for themselves you'll have to go up and clear the box.

Make or buy?

If you're confident of your skills, I'd recommend making your own. This is because almost all you'll find for sale are the tube-type boxes shown on the right. Making your own is about the only way to avoid these decidedly owl-unfriendly quarters. I'll go into why I think these are such poor designs on the next page.

Making a box gives the pleasure of seeing owls use something you've crafted with your own hands. You can also use a low-profile design that gives you a better chance of seeing your guests. In these designs the distance from the door to the floor is much reduced (though note that low-profile boxes are not recommended for Barn Owls).

An alternative is to get a friendly carpenter to run up one of the designs on these pages. It might cost a quid or two, but a well-made and maintained owl box will last indefinitely.


What type should I buy?

If you buy, you haven't much choice. The two "officially sanctioned" designs in the UK are the chimney (top right) and the letterbox (lower right), and they're the only types that are widely available. In the pic of the chimney box shown here the opening in the front is the cleaning hatch, which is closed in normal use. The chimneybox is open at the top and is meant to be slung under a sloping branch or fixed at an angle to a tree trunk. The letterbox has a roof and the entrance is near the top in the front panel. I don't like either design because of their many disadvantages for the owls. With its better weather protection (a roof) the letterbox is the lesser evil. I find it astonishing that anyone could recommend the chimney box design, period.

There's another real problem with the boxes that are sold. This is that although many retailers claim that their boxes are built to designs approved by the RSPB and BTO, they skimp on the recommended side dimensions, resulting in boxes that are too small. Don't buy a box with outside side dimensions less than 10 inches.

With most boxes on sale the choice is between the chimney (top) and the letterbox (below).

Where can I buy a ready made nestbox?

There's a list of boxes on sale on the internet on page 9. Unfortunately there are very few nice boxes, so you may end up wanting to make your own. Also, as I've said, there's a load of makers who ignore the RSPB/BTO recommended dimensions, and I'd give their boxes a decided miss. On top of basically bad designs and, in many cases, construction, these boxes are just too small and cramped for comfort.

What's the best type to make?

The photo at right shows what I believe to be an excellent design. It's being used in Holland and is a Dutch design, so I call it the Dutch letterbox. It's (fairly) simple to construct, provides plenty of floor space and is just the right depth. Go to this anchor on page 4 for materials and dimensions. Extensive construction details on page 4.3, plus pics of one of them being put up in its tree.

I like the design so much that I've made two of my own. These, however, have an essential fixture for all owl boxes — a ledge.

Thanks to A. van den Burg for the photo of one of his boxes.

What's the best place for a nestbox?

The ideal site for a Tawny Owl nestbox is 15-20 ft up a tree. However, they don't appear to be fussy and other sites could be tried provided they are safe (think rats, cats, martens in some areas, crows and human nest raiders. Squirrels often pester owls too). The tree can be any type -- deciduous or conifer -- though the bigger and smoother the trunk the better as attaching a square box to a round trunk can be a real problem. But having a box on a long stretch of bare trunk isn't a good idea — it's important that there should be branches within easy reach for the owlets to jump to when they leave the box.

Tawnies seen to prefer a site in a wood. Sites to avoid are isolated trees in fields. They seem to be quite happy with trees in gardens or places where there are other trees nearby.

Also consider factors such as exposure to weather -- particularly wind direction -- and sun. In a sheltered place such as a wood or group of trees these may not be important. A nestbox should be in a shaded place as it can get very hot in a box when the sun becomes stronger in May. Proximity to human habitation or activity doesn't appear to be a problem.

Don't put a nestbox anywhere near a road as this will greatly increase the chances that parents or children will be hit by a vehicle. 75 yards would be an absolute minimum distance, and the further the better. Tawny Owls often glide downwards after leaving a perch to pick up speed before starting powered flight, and if this means the male is at the end of his downward swoop as he crosses a road he has a high chance of being hit and killed. He does much of the food gathering when the female's brooding and comes in with goodies about once every hour during the night. If his hunting area is the other side of a road, that means he'll be crossing it at least 300 times during the two months from hatching to fledging, so a poorly sited nestbox could put him, and his family, at considerable risk. If there's a barrier between the nestbox and the road, or if the owls are known to hunt away from the road, that would reduce the risk. (See footnote.)

Footnote: In a French study of tawnies using 200 nestboxes, death through traffic accidents was a major cause of death for owls using boxes near roads, and turnover in such boxes was high. Owls living away from major roads lived on average two years longer. (Baudvin and Jouaire, 2003) As the average life span is about 5 years, that's pretty significant.


Which way to face the nestbox? My main consideration is the parents' obvious pleasure in communicating with each other during nesting. The female listens out for her mate while he is away and may call to him frequently. This has an obvious function in that it encourages the male in his hunting efforts. So I try to establish where the main hunting is done by listening at other times of the year and face the box that way. The main weather direction isn't often an important consideration as winds and driven rain aren't likely to be a problem at the relatively low height of a nestbox or in a sheltered garden. In our woods it isn't a problem at all.

Our main nestbox in the woods is some way from the house, so work on it can be quite a major undertaking. Here it's being put back up in autumn 2006 after cleaning and installation of a camera.

Planning ahead

Before deciding to go ahead with a nestbox it's a good idea to check that there really is a place you'll be able to put it up without too much difficulty. I.e. get your boots on, go out and identify a suitable site.

Basically you're looking for a place 15-20 feet up a mature or semi-mature tree. 12 ft would be just ok, but can you be sure it will be safe from raiders or vandals? For the same reason owls seem to prefer higher sites. 20 ft is about the upper limit simply because with most ladders it's difficult to work safely higher than that. If the tree's easily climbable above the top of the ladder, well and good, but remember you'll have to come down every time you drop something or need a tool you haven't taken up. (You'll also need to go back up over the years to do the things that an owl box needs to have done.)

The bigger the trunk the better as it's flatter, so to speak. Look for 9-12" diameter. Don't go much larger than 12" if you're using cord or wire to fix a box as you'll have difficulty getting your arms around bigger trunks. Boxes certainly can be fitted to less than 9", though you may end up with an attachment that rocks from side to side. Also, the less irregular (bumps and rough bark) and the more vertical the trunk the better.

Type of tree doesn't seem to matter. Oak (especially) and Scots Pine seem to be favourites, though there are many reports of tawnies using boxes in other types of tree. All the owls care about is having a safe place to rear young. There are several reports of successful nestboxes near houses and even fixed to the wall of a house.

Types of attachment are dealt with on page 5 and the actual business of fixing the box in place is dealt with on page 6. It's worth having a look at these pages as knowing what's to come may help in choosing a site.


In conclusion

If I've made it sound difficult -- well, it is and it isn't. It's just that there's a little more to think about, and rather more to do, than if you're putting up a box for a small bird species. There's nothing that a bit of commitment won't get you through. If you have a tawny pair around there's a very high chance that they'll use a box, and when this happens it's a rather wonderful thing. In fact during the two months of the breeding season you may find yourself thinking of little else.


BBC Tawny Owls using nestbox on YouTube

In case you missed the link on the index page, there's a good 9-minute clip from a BBC natural history programme on YouTube. Filmed in the Forest of Dean, shows a tawny pair raising a family of four with help from neighbouring humans. Tawny Owls - BBC 25.09.07

Piped owls in Cambridgeshire -- the joys of having owls in your nestbox

A family living near Peterborough in east central England have had tawnies using a nestbox for 23 years. Two years ago they took down the old box and put up a new one fitted with a camera plus microphone. Making the connection to the house needed 100 m of cable as the tree is at the end of quite a long garden, but now the owls can be watched in comfort any time they're there and their calls echo around the whole house!

What's interesting about the location of this nestbox is that not only is it in the centre of a small town, but the surrounding countryside is almost entirely flat agricultural land with little, if any, woodland and few mature trees in the hedgerows. The owner says there are about 100 trees, mainly limes and silver birch, immediately around the garden, so it's from these that the owls presumably hunt.

Anyway, that should be encouragement for anyone living in a similar area. If you do live in a small town, or in a relatively treeless area, and there are tawnies around, there's little doubt you're doing them a good turn by putting up a nestbox. The trees in urban areas are nearly always carefully manicured by the council, meaning that there are unlikely to be natural holes in them of sufficient size.

As to Tawny Owls living in towns, there is apparently at least one pair in Regent's Park, London, and another in Buckingham Palace garden! Details as of about 2000 are given in a Westminster Council Biodiversity plan (100.70 K) (pdf). A 1996 estimate suggested there might be up to ten pairs altogether in Inner London.

Even as I was putting this Nestbox section together the Peterborough pair began a family. Jolly good, but the remarkable fact is that this was in January 2007. Tawnies usually breed in or after mid-March. Thanks to the owner and his webcam I was able to follow subsequent developments from my desk in London! The illustrated story of the Peterborough owls and their successful early breeding attempt has moved to its own section here: The Cambridgeshire Tawnies 2007.

Taking down the old box in a walnut tree at the bottom of the garden.

20 Jan 2007: The female sitting on the first egg


Also see the Tawny Owl Nesting Diary 2008 on this website. It's an illustrated account of a pair of our local owls starting 19 March 2008.

Register your nestbox with the BTO and upload observations

The British Trust for Ornithology (BTO) now have a scheme for registering nestboxes for many bird species. Until I registered my two boxes on 22 Feb 2007 there were no Tawny Owl nestboxes in the scheme. In fact the only owl box that was registered then was a Little Owl box near Loughborough in Leicestershire. Yes, not even any Barn Owl boxes. So there's an opportunity.

As of 22 Feb 2007 there were more than 4,500 nestboxes in around 2,800 gardens have been registered. The numbers vary depending on which page you look at. Your nestbox doesn't have to be in a garden, by the way, but if yours isn't you'll still have to answer lots of garden-related questions when you register a box. Ah well.

April 2008: As the result of some email correspondence between me and the BTO, I'm assured that this summer they'll be addressing one of the (to me) main drawbacks of the Nest Box Challenge database — that us humble data loggers can't view each other's entries. At the moment you can only view your own data entries, and I for one would very much like to see what other owlers are finding! Other features I suggested are: the ability to edit entries after you've submitted them (to add information or correct mistakes); the ability to make second (and more) entries for the same day; and the ability to view more than one day's entries at a time.

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Tawny Owls:

First things, page 2

The perfect Tawny Owl box? A Dutch enthusiast has built and placed a dozen of these roomy nesting sites in woods near his home. Made to a Dutch design, the floor area gives a mother and her brood plenty of room, and the box is not too deep like so many sold here in Britain. More details here on page 4. (Photo A. van den Burg.)