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, design and build your own. Apart from the pleasure of seeing owls use something you've crafted with your own hands, there are several problems with the commercial tawny boxes sold in this country. These I'll go into on the next page, but one obvious problem is that their design means you aren't going to see much of your guests. Otherwise, of course, you'll have to buy, though I suppose you could get a friendly carpenter to run up a better design for you. It might cost a quid or two, but it's worth it if it lets you see the owls. And a well-made and maintained owl box will last indefinitely. (How to modify a chimney box to get more space is shown on page 7.)

What type should I get?

In the UK the two "officially sanctioned" designs are the chimney (top right) and the letterbox (lower right), and they're the only types that are widely available in this country. The chimney 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 lesser evil may be the letterbox. Neither box will allow you to see anything that happens inside.

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

One box I can recommend is designed and sold by the Barn Owl Centre in Gloucestershire. I don't have my hands on one, so can't comment on the build. At £45 + £12 delivery it's more expensive than the competition, but the design is owl-friendly so it's definitely worth a try. The only problem I've heard (from one correspondent) with this type of low-profile design is that tawnies appear to prefer deeper boxes if they're also available. Here's the BOC page for this box. You may find a letterbox type in the BOC shop too, but I'm told they're stopping production of such boxes as they too consider them unsuitable.

Some of the UK boxes for sale on the web are listed on Page 9: Commercial box review.

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

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. I've only just come across it, so can't go into great detail, but it's 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. (Photo © A. van den Burg)

Where can I buy a ready made nestbox?

About the only box I can recommend with some conviction is made and sold by the Barn Owl Centre in Gloucestershire -- see the photo below. This also appears to be the only simple box type sold via the internet. It offers ample room, but a disadvantage is that it's on the heavy side. It's also not as cheap as most others on sale.

The most generously sized letterbox is sold by Wheatear (box page here). With side dimensions of 12 in by 12 in, it's also the only box that's offered in 12 and 18 mm ply. Prices are very reasonable.

Jamie Wood Products (click on OWL BOXES) makes a chimney box to the RSPB/BTO recommended dimensions, but the letterbox is areally smaller than these organisations recommend. They cost £25 to £35. As I consider the chimney design flawed in general and this letterbox is a shade to small, I find it diffucult to recommend either. In their favour is that they are nevertheless larger than any of the other tube-type boxes apart from Wheatear's (above).

I would recommend not to buy boxes by the other British retailers listed on my Page 9 as they ignore the RSPB/BTO dimensions and their boxes are far too narrow, giving mother and chicks too little space.

A tawny des res -- the carefully thought-out nestbox from the Barn Owl Centre. They say it's designed for a range of raptors, including the Tawny Owl, but as far as I'm concerned it's a lot nicer than the two shown on the right and meets the tawny's needs well. I'm told that tawnies do use them. You may not see the owls inside, though. For that a central entrance is needed (more later). More details of this box on page 9.

Photo © Gloucestershire Barn Owl Centre.

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 may 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. A long stretch of bare trunk isn't such a good idea -- there should be branches within easy reach for the owlets to make wing-assisted jumps to when they leave the box. 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 will almost certainly be hit and killed. He does all the food gathering during the nesting season and comes in with goodies about once every hour for much of 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.)

My main consideration in choosing which way to face a nestbox is the parents' obvious pleasure in communicating with each other during nesting. The female listens out for her mate while he is away and calls to him fairly 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 entrance 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.

Right: 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.

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 (BTO) that's pretty significant.

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 higher safely. 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've forgotten. Remember too that you'll 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 10" diameter plus. Boxes certainly can be fitted to less, 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. A box can be fitted across two branches, too, though that can get a little tricky as ideally you want four points that are in nearly the same plane and, preferably, a vertical plane.

Type of tree probably doesn't matter. All the owls care about is having a safe place to rear young. I haven't tried, but I guess they'd use a box that was fixed far enough up the wall of a house.

Types of attachment are dealt with on page 5 [to come] 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 [when they're ready] 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 consider, and rather more to do, than if you're putting up a box for tits or a bird feeder. There's nothing that a bit of commitment won't get you through. There's a very high chance that Tawny Owls will use a box that's put up for them, and having a pair use one is a rather wonderful thing -- see the story below. In fact during the two months of the breeding season you may find yourself thinking of little else.

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

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's been registered so far is 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 more than 4,500 nestboxes in around 2,800 gardens have been registered. The numbers vary depending on which page you look at.

March 2008: Unfortunately the Nest Box Challenge pages are a bit poorly done and data entry is a tedious business. Nor can you change any entry once it's in, so if you make a mistake (like entering info for the wrong box) that's it, it's in the database for ever. Astonishingly there seems to be no field for entering the species you're observing -- you're just left to realise that you have to mention it somewhere in your daily data entries. One result is that my three tawny boxes, all registered, fail to show up on the Results map for the species!!! Another big disappointment is that you can't see data entered by others, so for example I can't compare my results with what other tawny nestbox owners are finding. Altogether a clunky and restrictive section of the BTO's website.

So I wonder if there are others whose boxes aren't showing up.

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