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 that give a nesting female a maximum of just over 12 inches to lie across. 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 brief, they are too deep and narrow, they have a slippery interior (unlike a hole in a tree), and they have no ledge. The chimney box, with its open top, adds to the problems by exposing the interior to rain. As of mid-2009 I have stopped listing almost all boxes made to the tube design as my view is that they are both unpleasant and unsafe.

How much room does a Tawny Owl need?

An adult Tawny Owl is 14 inches or more (up to 18 in) from head to tail. Quite simply then that's the minimum a female needs if she's not going to have to pull back her head or press her tail feahers up against wall to fit. Remember that the female has to spend about 23 hours out of 24 in the nest for as long as six weeks.

I've used the internal diagonal as the critical measurement in comparing 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 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). Sides of 12 inches (30 cm) are the minimum you should be looking for.

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.)

Dutch letterboxes

No question that these are the best boxes. They are not cheap, but the owls like them and if you look after them properly they will last more or less indefinitely. Two have come on the market recently.

NEW 2009

Valley Wildlife, Burnley, Lancs

Tawny Owl box to dutch letterbox design.

Dimensions: 11" deep x 14" wide x 24" high (at back).

Internal diagonal ~16".

Materials & constrn: 12 mm exterior ply on batten frame with solid timber back mount. Design is modular to make tree-fixing easier. Finish: Cuprinol wood preserver.

Price: £98.00 plus carriage of £15. Delivery 28 days. Can be installed for you.

Contact: Ian Waddington or David Berry: valleywildlife [AT] btinternet.com

Address: Valley Bird Boxes, 5 Hambledon View, Read, Burnley, Lancashire, BB12 7PD

This is an excellent and cleverly designed box that's made to last. The dimensions are perfect. See photos and more details on my page here. Recommended.

NEW 2009

Riverside Woodcraft, Tamworth, Staffs

Tawny Owl box to dutch letterbox design.

Dimensions: 600mm high x 350mm wide by 350mm deep (approx 24" x 14" x 14"). Entrance: 150mm x 125mm (6" x 5"); ledge: 350mm by 200mm (13.7" x 8").

Internal diagonal ~18".

Materials & constrn: Made of "solid redwood" (i.e. pine). Cleaning hatch in lower part of front and removable roof. Fixing to tree by back plate. Two colour options, light and dark (shown in pic), and an untreated version For how the box is constructed, see pic below.

Price: £84.95 + £5.95 delivery charge.

Comments: This is a generous-sized box with a very roomy interior — 3" more front to back than the Valley Wildlife box. The downside of a large box is that it can be more difficult to put up. Recommended

Riverside Woodcraft nestbox page Tawny Owl box is several clicks down page.

Left: A Riverside box under construction.

Tube-type letterboxes

These are the only boxes of this type with reasonable dimensions that I've found for sale

Wheatear, York

"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 (lower photo) 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.

Wheatear nestboxes 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, even if sealed or weatherproofed. 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 in at around £32 before p&p.

Simple box type

The Barn Owl Centre in Gloucestershire make a box that can also be used for tawnies . . .

The Barn Owl Centre of Gloucestershire, Hemsted, Gloucester

Designed for Barn Owls, but 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. (Info from 2007)

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

Materials & constrn: Timber; assembly with screws and nails?

Attachment: Nailed or screwed back bar.

Nestbox webpage. Box retails for £47 + £12 carriage (June 2009). Boxes can also be put up for you for £40 (currently Glocs area only — see "Nestbox Service" link for details).

With over 1,000 boxes of various types now up, the people at the Barn Owl Centre can claim a lot of experience of what owls do and don't like! This general owl box was designed after they decided to stop using tube-type boxes for Tawny Owls. Basically a Barn Owl box, it's the only low-profile design I've seen on the market. Plenty of room, but the weight and size call for care in putting it up. The absence of a ledge is a disadvantage — it should have one.

There are some important caveats, though . .

1. This box is the minimum depth for the safety of tawny chicks (I'd put in a bit more depth). Another organization, the Devon Barn Owl Trust, also with considerable experience, has decided to stop using low-profile boxes like this for Barn Owls as they have found them to be unsafe for these owls. For further details of the Trust's views, go to this anchor link on my website—along with discussion of the use of shallow boxes for Tawny Owls, you'll find a link to the Trust's own page on Barn Owl nestboxes. I strongly advise you to read this before making a decision.

Having said that, we have had no tawny chick safety problems with our own low-profile box (5 chicks in two breeding seasons). The odd thing is that if the chicks can see out of a box they make no premature attempts to leave.

2. I have a big problem with the absence of a ledge. A ledge is important for the safety of chicks when they emerge in the days before fledging and should be mandatory on all boxes for Tawny Owls.

3. The BOC box is quite heavy and bulky, and some may find it difficult to fix in a tree (the BOC claim they are relatively easy to put up). You can use the Nestbox Service they offer if you're in the Gloucestershire area.

4. Someone who's tried both shallow and deeper boxes found that tawnies may prefer the latter.

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

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

James Wood Products, Polegate, E. Sussex

"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.

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.

Contact: See below.

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.

James Wood Products, Polegate, E. Sussex

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.

* 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.

Contact: James Wood Products (Nest Boxes) Ltd, Cross St, Polegate, East Sussex BN26 6BN. Tel: 01323 483813

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! As I find myself saying until I'm blue in the face, all owl nestboxes should have ledges. They're essential for the safety of the chicks.

(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. There's little difference between the American and Dutch letterboxes — they're essentially the same thing.

March 2009: Valley Wildlife are now making the Dutch letterbox shown at the top of this page. For a detailed illustrated description of this box, see my page here.

(Links on this page checked March 2008; search for web-sold boxes last done summer 2007. Latest revision April 2009)

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