A review of some Tawny Owl nest boxes sold in the UK

THE TAWNY OWL NESTBOX MARKET here in the UK is dominated by two designs published and approved by the two big bird organisations, the Royal Society for the Protection of Birds (RSPB) and the British Trust for Ornithology (BTO). Both are tube designs with sides of 10 inches. I have given the reasons for my misgivings about these designs in detail on Page 3: Types of nestbox and on Page 11: Approved designs. In a word, they are too deep and narrow, and they have no ledge. The chimney box, with its open top, adds to the problems by exposing the interior to rain.

An adult Tawny Owl is 14 inches or more (up to 18 in) from head to tail. From the top of her head to the tips of her folded wings is a minimum of 11 in, so as she can raise her tail that's the least a small female will need to lie comfortably across the diagonal of the box. Less, and she's going to have to twist or pull back her head to fit. Remember that the female has to spend about 23 hours out of 24 in this position for almost six weeks non-stop.

So, I've used the internal diagonal as the critical measurement in comparing the boxes. This has been calculated from the manufacturer's dimensions (assumed to be exterior unless otherwise stated) by subtracting one inch from the side dimensions to allow for the thickness of the wood (i.e. 1 in = 2 x 0.5 in). This will be (very) slightly unfair to boxes made from 9 mm ply, but the difference from the actual diagonal will be minimal. The RSPB and BTO designs both give an internal diagonal of about 12.5 inches.

I would recommend you don't even consider a box with a diagonal less than 12 in (30 cm) as it is simply unkind to the nesting female. That rules out boxes with sides less than about 10 inches (250 mm).

A conservation officer in charge of several hundred owl boxes described the tube designs to me as "diabolical". So why do we have them? The only reason for their existence is that tawnies are cavity-nesters, and the tube-type box is supposed to mimic a hole in a tree. Well, I don't doubt that this patient and long-suffering bird will nest in some pretty confined natural sites if that's all that's available. The point is you are making a choice, and you don't have to add to the hardships of a tawny's life.

Why the RSPB and BTO don't promote a safe, pleasant design like the American letterbox and with sides just 2 inches longer than their present designs I do not know. The dreadful chimney box should be abandoned altogether.

Right: This is where a tawny mother will nest if she and her mate are lucky enough to have a hollow tree in their territory. It's a far cry from most British boxes. (Photo courtesy of Darkec, Hrsovo, Croatia.)

Boxes with exterior side dimensions of more than 10 inches (25 cm)

These dimensions give an internal diagonal of 13 in or more. Boxes with such floor dimensions are hard to find.

Spring Into Action, Wildlife CCTV Specialists, Clayhidon, Devon

Tawny Owl box; Barn Owl version also available

Dimensions: 24" high x 14.5" wide x 14" deep (61 x 37 x 35.5 cm). Weight: 11.5 kg

Internal diagonal: ~18.5 inch

Materials & constrn: 15 mm (0.6 in) tongue & groove

Attachment: details to come

Website: www.wildlifecctv.co.uk; email: mail@wildlifecctv.co.uk

A new venture by Mike Babb, Spring Into Action plans to provide plain and camera-equipped versions of this roomy box, which is based on the excellent Dutch letterbox design (see my page here). These quality boxes don't come cheap: the cameraless version, which will be available soon, sells for just over £100 incl p&p. Camera-equipped boxes will be available in autumn 2008 (prices to be announced).

I'm delighted that someone should now be making an owl-friendly box of this type, and as I had a small hand in advising Mike on the design of the tawny box you'll find a dedicated feature on the next page.

The Barn Owl Centre of Gloucestershire, Brockworth, Gloucester

Mainly Barn Owl box, but also suitable for Tawny Owls.

Dimensions: 600 x 400 x 300 mm (l x w x h); 24 x 16 x 12 in. Door: 6 in x 6 in. Weight: 15 kg.

Internal diagonal: 27.5 in (open space . . there's no internal wall).

Materials & constrn: timber; assembly appears to with nails.

Attachment: nailed or screwed back bar.

Webpage (shop). Box retails for £45 + p&p (Mar 2008).

Recommended, but weight and size call for care in putting it up.

With over 1,000 boxes of various types now up, the people at the Barn Owl Centre have a lot of experience of what owls do and don't like! This general owl box was designed after much thought and because the BOC decided to stop using narrow tube designs for Tawny Owls. Basically a Barn Owl box, it's the only simple box design I've seen on the market. Largely because of its generous internal space, it's also the only box apart from Spring Into Action's above that I can recommend with anything like enthusiasm. Some caveats, though: 1. Someone who's tried both shallow and deeper boxes has suggestd to me that tawnies may prefer the latter; 2. If you buy, check that the box has a ledge as pics on the website show boxes without ledges (a ledge is essential); and 3. These are quite heavy, bulky boxes and some may find them difficult to put up. The BOC claim they are relatively easy to put up.

Wheatear, Lincoln/York area (no address given)

"Tower box" for Tawny Owl, Little and Barn Owls, Jackdaw, Stock Dove.

Dimensions (internal): 300 mm x 300 mm x 900 mm (650 mm to entrance). Side inspection door 300 mm x 200 mm located 200 mm above base. (Imperial: ca 12 in x 12 in x 35.5 in; 25.5 in to door).

Internal diagonal: 16.7 in.

Materials & constrn: available in 12 and 18 mm plywood (upper photo) and 12 and 18 mm chipboard (below) and in three finishes: "gold", red and brown. Also with no treatment. Not only that, boxes can be supplied assembled or as flat-packs. Nails used for assembly. (Pics at left show 12-mm versions)

Nestboxes made from 18 mm ply weigh 15 kg.

Attachment: 5 m metal band pack available as extra purchase. Band has 5-mm holes along its length for screw fixing to box and tree.

Nestboxes on this page. (Warning: site behaves peculiarly in my browser)

Comments: Recommended apart from lack of ledge -- you should add one if you buy.

If these really are internal dimensions as claimed, this is the most generously sized deep letterbox I've seen so far and is quite adequate for a Tawny Owl. Wheatear recommends the treated heavy-ply versions for longevity, and I would agree. Using chipboard outdoors sounds a bit dodgy to me. The metal chain attachment is novel. Prices are reasonable but you may find the price charts confusing! You have to work out the price after choosing from a range of options. A treated 18-mm ply box plus fastenings would come at around £32 before p&p.

That's all the boxes I can recommend. Those that follow are just included for review purposes.

Borderline boxes with exterior side dimensions of ~10 inches (25 cm)

These dimensions give a rather cramped internal diagonal of around 12 in.

Jamie Wood Products, Framfield, E. Sussex (not in business?)

"All our nest boxes are made in accordance with the specifications approved by the RSPB, British Trust for Ornithology and are used by conservation groups throughout Britain"

Dimensions: 25cm x 25cm x 80cm (10 in x 10 in x 31.5 in).

Internal diagonal: 12.7 in

Construction: 9 mm exterior plywood, glued and pinned.

Attachment: nail or screw through holes in back panel.

Jamie Wood eBay store (not in action when checked March 2008)

Comments: As for all open-topped chimney boxes, not recommended, although the side dimensions are as recommended by the RSPB and BTO. The letterbox (below) gives better protection, but as sold it appears to have less floor space by quite a margin.

I bought one of these boxes for investigation and (later) to see if it was possible to convert into a roomier, camera-equipped box -- see Page 7: Modifying a chimney box. There are pics of my tester in this box on Page 3: Types of nestbox.

Jamie Wood's letterbox (below) is difficult to place sizewise as one I bought is significantly smaller than claimed and than the bird organisations recommend. Sides of 30 cm x 27 cm are stated on the website; my own example, bought recently, is 25 cm x 24 cm (9.8 in x 9.5 in). This would put the box at the top of the group with sides less than 10 in, which I find difficult to recommend.

Jamie Wood Products, Framfield, E. Sussex (not in business?)

Dimensions (stated*): 30cm x 27cm x 80cm (11.8 in x 10.6 in x 31.5 in). Door: 12cm x 15cm (4.7 in x 5.9 in).

Internal diagonal: 14.5 in (based on dimensions stated); purchased sample was 12.2 in

Construction: 9 mm exterior plywood, glued and pinned.

Attachment: nail or screw through holes in back panel.

Jamie Wood eBay store (not in action when checked March 2008)

* Actual side dimensions of one bought in autumn 2006 are 9.8 in x 9.5 in, giving an internal diagonal of only 12.2 in. If this box was made to the dimensions stated on the website I'd give it a qualified recommendation.

Next, a box from Sweden that only just makes it . . . Internally this box looks to be a mere 6 inches from front to back, but its external width of just over 1 ft means that it scrapes by with an internal diagonal of 12 inches. So I include it out of interest as a non-UK design but cannot really recommend it -- it's just too small and, again, it should have a ledge.

Bankeberg farm, Småland, Sweden

Tawny Owl box (web page for box)

Dimensions (external): 31.5 cm (12.4 in) wide by 20.5 cm (8 in) deep. Entry hole is 14 cm (5.5 in). Height not stated.

Internal diagonal with 1-in wood shown in pic: 12 in

Description: "The front can be opened and the inside is lined with wooden ribs to help the young owls find their way out of the box. It is assembled using screws. The roof is made of 12-mm water resistant plywood. We supply the box treated with environmentally safe brown-tinted oil which provides good long-term protection from the weather. The rear section is made of oak with good resistance to rot."

Attachment: "When setting up the box, first screw the back panel in position, and then hang the box on the two bolts proved and fix with the corresponding nuts."

Although in southern Sweden, this family-run farm will export the boxes anywhere in Europe. Unfortunately the box is 50 euros (incl. Swedish VAT at 25%), which with mailing costs of about 34 euros won't make it very competitive in the UK.

These people have a gorgeous cottage to rent at very reasonable rates. You could book a stay and avoid the mailing costs for the box!

Boxes with exterior side dimensions of less than 10 inches (25 cm)

The boxes listed in this section do not comply with RSPB and BTO recommended dimensions.

I suggest you do not even consider boxes with side dimensions of less than 10 inches. For example, a box with sides of 9 in has an internal diagonal of about 11.5 inches, which is too small for an adult female Tawny Owl (14-18 inch overall length). The boxes here are listed in order of decreasing diagonal.

All of the four British chimney boxes listed below have an internal diagonal that's a full 2 inches less than would be given by the dimensions recommended by the RSPB and BTO in their plans (shown near the top of page 11).

Schwegler Vogel- und Naturschutzprodukte GmbH, Schorndorf, Germany

Described as Tawny Owl box; stated also to be suitable for Stock Dove, Jackdaw, Goosander and Goldeneye.

Dimensions: "Interior of nesting chamber: Ø 20 cm; Width of entrance hole: 110 x 120 mm". Height not given. In inches I take it that's an 8-in interior side with an entrance of around 4.5 in. This doesn't seem consistent with the accompanying photo.

Internal diagonal: ca 11 in

Material: Schwegler's proprietary woodcrete.

Attachment: Proprietary suspension (see photo). Possibly unstable.fixing for box.

Front panel removable.

Schwegler website

Available in UK from Jacobi Jayne (page for owl boxes is here), Alana Ecology and Wildlife and Countryside Services (see entry in next section).

CJ WildBird Foods Online, Upton Magna, Shrewsbury

Dimensions: Height: 76cm (29.7ins) Width: 22cm (8.7ins) Depth: 20cm (7.9ins). (Imperial conversions as given by retailer)

Internal diagonal: 10.4 in

Attachment: "Straps for fixing the box to a tree are available from many DIY and camping stores."

Nestbox page (no other model offered)

Comments: CJ WildBird Foods is linked from the BTO Garden Bird Watch pages as it is a sponsor and co-organiser with the Trust of Garden Bird Watch. One wonders therefore why this box is made with significantly smaller side dimensions than the BTO's recommended (and already cramped) 10 in by 10 in. Box shown in photo is attached at too steepan angle.

The Nestbox Company, Kington, Herefordshire

"Nesting boxes thoughtfully designed for their inhabitants"

Described as Tawny Owl nesting tube, but also stated to be suitable for Little Owls, Doves, etc.

Dimensions: 20 cm x 22 cm x 76 cm (8 in x 8.7 in x 30 in). Height to exit: 30 in.

Internal diagonal: 10.4 in

Attachment: not stated, but photo shows what appears to be a single screw at top of back panel

Other details given: "Exterior quality resin bonded ply, drainage holes, manufactured with surface sunk nails to resist rusting, coated with a non-toxic water repellant finish." Photo appears to show internal corner battens.

Nestbox page (website out of action when checked March 2008)

The Nestbox Compay doesn't sell other Tawny Owl models. Photo shows box attached at an incorrect angle (too steep). If there are internal corner battens, they will further restrict the space for the owl.

Wiggly Wigglers, Blakemere, Herefordshire

Tawny Owl box

Dimensions: 760 x 200 x 220 mm (30 in x 8 in x 8.7 in). Height to exit: 30 in.

Internal diagonal: 10.4 in

Material: plywood

Attachment: not stated, but says "Straps not included", so presumably intended to be wired.

Website: go to Shop > Birdboxes > Tawny Owl Nest Box.

This appears to be the same model as sold by The Nestbox Company but without the internal corner battens.

Wildlife & Countryside Services, Penmachno, North Wales

"Tawny Owl Nest Box" (this is a chimney box)

Dimensions: H 755mm x W 200mm x D 218mm approx. (ca 30 in x 8.6 in x 7.9 in)

Internal diagonal: 10.3 in (my calculation, as for other boxes)

Weight: 4 kg

Drainage: 9 holes in the floor of the box

Attachment: Various methods are suggested in the information sheet that is sent out with the individual nestboxes, eg. battens are screwed to the box to suit the type of tree or the box could be wired to a diagonal branch of the tree, etc.

No dimensions given on website. Details here courtesy of WCS.

Webpage for nestboxes

Wildlife & Countryside Services, Penmachno, North Wales

"Large bird nest box" . . . "Suitable for woodpeckers, owls, pigeons, doves, jackdaws & kestrels"

Dimensions: H 525mm x W 205mm x D 189mm approx (21 in x 8 in x 7.4 in).

Internal diagonal: 9.5 in

Weight: 3 kg

Drainage: 9 holes in the floor of the box

Attachment:Screw holes provided on the back board.

No dimensions given on website. Details here courtesy of WCS.

This model is apparently intended for Little Owls and is not suitable for Tawny Owls.

Webpage for nestboxes

How does a Tawny Owl fit into these boxes?

Not easily. To show what a 10.5-inch diagonal means for a mother Tawny Owl I've done the diagram on the right. It's for 9-mm ply boxes. Remember that between 2 and 4 growing chicks are going to have to fit in too. IMO it's horrible.

In the diagram below you can compare the BTO and RSPB recommended dimensions (blue) and those used in these boxes (red).

It's worth pointing out that owls don't brood eggs like penguins -- standing up! Like most birds they like to lie flat across them. To fit, the mother has to crook her neck back and have her tail vertically against the wall, and she has to stay in that position for nearly 6 weeks!

Battery Owls anyone?

If you buy a box with 8.5 in external sides, that area inside the grey box is what an owl like this is going to have to squash herself into.

Boxes for which insufficient details are given

I'm hoping to get details on these.

Birdcam, North Kessock, Inverness, Scotland

Described as an "Owl box . . . best suited for Tawny Owl".

No dimensions given.

A camera-equipped box -- comes with "colour/black and white camera, 20 metres of cable, a power supply unit and audio and visual plugs which connect straight into your television or video". IR light not stated, but appears to be available. At £220 fully equipped, a pricey box (the AV kit includng power and cable is sold for £100).

Website: Home page; Owl box page; Prices page (gives some details of AV kit).

BirdBoxTV, no address given

Appears to be a chimney box.

No dimensions given.

Box shown sold without camera for £55.

Website: Home page; Owl box page. Website appears a bit unready -- e.g. no contact form comes up in my browser on the Contact page!

August 2007: Site no longer available. Will leave entry up until end of year in case BirdBoxTV reappears. Still unavailable March 2008.

Just Green Ltd, Burnham-on-Crouch, Essex

Appears to be a chimney box (i.e. top entry).

Dimensions: 76 x 20 x 45cms (20 cm is presumably a bottom side measurement but not clear whether it applies to both sides. If it is an 8 in by 8 in box, the internal diagonal is about 10 in, putting this box among those with the least floor space.)

"Handcrafted in our UK workshops from Forestry Stewardship Council approved timber, specifically designed for the Tawny owl. The box can be attached to trees in gardens or in woodlands at angle of 45 degrees or less to the vertical."

Website. Also sold on Amazon UK

If this is a chimney box (opening at top), photo shows it attached incorrectly.

Mar 2008: Just Green are now showing a new pic of what appears to be a simple chimney box. You'll need to search (the site) on "nest box" to find it.

The Owl Box, Llangaffo, Anglesey

Tawny Owl box

Tawny Owl box page

Dimensions: "500mm high when fixed; 220mm overal depth; 320mm hight; Letter Box Opening 175mm depth (internal.)"

Constrn: 9 mm exterior plywood.

Attachment: Not stated.

Can't figure this or the photo out at all! A novel-looking box. £35.50 plus p&p.

Bird Ventures, Holt, Norfolk

"Tawny Owl Nesting Box"

A standard chimney box, no dimensions given.

Description given: "A tube shaped box made from light plywood making erection easy. The box has an inspection hatch and should be placed with the entrance hole facing up at a 33 degree angle on the trunk of a tree or large branch."

Webpage for this nestbox

Other nestbox retailers with products not yet reviewed here

Traditional Nest Boxes (Aldersley, Wolverhampton; pine chimney box, photo but no details). Eco-Watch camera-equipped nestboxes (Heligan, Pentewan, St Austell, Cornwall; no details of owl box(es), but a large range of equipment, some pricey. In a composite photo of their boxes I couldn't see a specifically Tawny Owl box).

Why can't we have a sensible box like this in the UK?

The pic below left shows a particularly nice example of the American-style letterbox, usually put up for Barred Owls. Recommended dimensions for this slightly larger owl are 14 in x 14 in x 28 in (WildBird Magazine). If the sides were reduced to 12 in, made out of 0.5 in wood that would give an internal diagonal of about 16 inches. This is shown in the diagram on right.

What I like about the US box is that it isn't so disproportionately deep as the "official" UK designs. Combined with its more spacious floor size, this makes for something altogether more owl friendly . . . no least for the chicks when they need to exercise and, later, leave the box.

I'd still like to see a ledge on it though!

(Photo from DruidLabs nestbox pages ; box apparently constructed by Wildlife Preservation section of the Jackson Pathfinders.)

(Since writing this I came across the "Dutch" letterbox design shown on page 4, and Mike Babbs in Devon is using it as the basis for the boxes he is now selling -- see Spring Into Action at top of this page. There's little difference between the American and Dutch letterboxes -- they're essentially the same thing.)

(Links on this page checked March 2008; search for web-sold boxes last done summer 2007)

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