More swift boxes in Milton, Cambs

We already reported on Clarke Brunt's Swift boxes, where he had 6 breeding pairs of Swifts in 2015. Our recent successes with installing internal nest boxes in roof spaces convinced Clarke that he could do the same. Although there are no new ideas here, this is another example of a well executed installation.

by Dick

The location is perfect, right on Milton High Street and opposite the Lion & Lamb public house, where people sit out on summer evenings. The Lion & Lamb can expect increased custom from Swift nuts this summer and all future summers!

The project is very similar to what we did in Newnham. Again it was a Victorian solid wall, where removing a header was an easy way of making a hole through the wall. The same cast moulded concrete inserts were used for the entrances.

This time the boxes were made with hinged doors on the back, but were constructed so that these can easily be replaced with perspex backs if so desired.

This project was implemented by Bill Murrells and Clarke himself, with a bit of help from me.

The following pictures are self explanatory.

The view from the Lion & Lamb

3 entrances on the right hand side

Detail of a single entrance

6 boxes neatly installed

3 boxes on left side of gable

Close up of a single box

#inserts
#Cambridge

Circular entrance inserts

We have been quite successful in retrofitting half brick-sized entrance inserts in brick walls, either by removing a header from a solid wall (here), or cutting an entrance in a cavity wall (here). We here present an idea more suited for inserting in a rendered cavity wall comprising building blocks.
[I updated this post in Sept 2017 to show the entrance piece proud of the mortar]

by Dick

The mould is made out of a 50mm piece of a pipe 102.5mm
internal diameter. The entrance formers are 3D printed.

Builders are accustomed to making circular holes in walls to fit such things as ventilation grills and extractor fans. So this idea may be preferred by some builders, even in brick outer walls.

Michael Osborne did something similar here.

We have used the same 3D-printed former that we used for the half brick entrances, but this time we made a mould out of a piece of 4 inch pipe.

The internal box could either be embedded in the inner wall or inside the inner wall, typically in a roof space, accessed via a pipe.

Although we have not used this idea on a real project yet, we thought it worth sharing.

Computer generated pictures below:

Outside view of insert

In this case, the nest box (back removed) is inside the roof-space  .

Alternatively the nestbox could be embedded in the inner wall, spanning the cavity.

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#Cambridge

Owlstone Road, Newnham, Cambridge

In 2011,  we installed two 4-box Swift cabinets on 2 houses in Owlstone Road, Newnham. As in many places over the years, a street with a vibrant Swift population had been reduced to virtually nothing. The first Swifts probably occupied the cabinet on Pam and Vic Gatrell's house in 2014, but they were away for much of the summer, however in 2015, 2 pairs were definitely in residence, and one of them raised 2 chicks. 

by Dick

Two chicks looking out of the cabinet. Photo Vic Gatrell

Not being satisfied with this, Pam and Vic wanted more boxes. While we could have suggested a second cabinet, instead, we took a good look at the structure of the gable end, and suggested built-in boxes.  

The gable wall is 2 bricks thick, with no cavity and is built in Flemish bond: a sequence of headers and stretchers. Removal of a header makes a hole all the way through the wall. This was relatively easy, as the bonding was soft lime mortar.

Two entrance pieces and their moulds

With previous experience of retrofitting entrances fabricated out of airbrick liners, (here and here), this time we decided to try something different, with entrances cast in a mould using a 50:50 cement/sand mixture. 

The mould was made on a 3D printer. This meant the hole could be made to a fine tolerance, with dimensions 65mm x 29mm on the inside and 68mm x 32mm on the outside. Thus it was slightly tapered, allowing easy extraction from the mould and any rain drops would tend to flow out rather than in.

Casting entrances in a mould is a lot easier than slicing up airbrick liners.

Pam and Vic own the part of the wall
left of centre. Photo Pam Gatrell

Apart from manufacturing the entrances, the only other thing we did was to build the first nest box. We then handed over to Newnham Property Services who fitted all 6 entrances in the wall, built the remaining 5 boxes and fitted them inside the roof-space.

The work also included making a trap-door from an upstairs bedroom into the roof-space.

The end result is very pleasing, and bodes well for the return of a thriving Swift colony in Owlstone Road.

The following pictures should be self-explanatory.

[For Newnham Property Services, contact Marek on npscambridge@gmail.com phone 0773 137 6154]

6 new entrances; the natural colour of the cement/sand mixture
matches the brick colour remartkably well. Photo Pam Gatrell

Design drawing for the nest boxes. All boxes are fitted with a perspex back.
The perspex is held in place with slots top and bottom and slides out sideways

6 boxes inside the roof-space. Photo Pam Gatrell

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New houses for people - and for Swifts

A new social housing development by T J Evers, on behalf of Sanctuary Group, of twenty affordable houses in Northumbria Close, at the northern end of the village of Haddenham in Cambridgeshire is now complete. As it is a greenfield site, with much of natural history interest in the surrounding area, the developers agreed to incorporate biodiversity enhancements in their plans.

An environmental impact assessment of the site produced a record of Great Crested Newt. However, in consultation with Haddenham Conservation Society, a provision was written into the recommendations written by the eco-consultants, MLM, and subsequently into the planning approval requesting the installation of nestbox accommodation for bird species known to nest in buildings. In the event, this meant primarily Swifts.

Jake Allsop and Dick Newell of Action for Swifts, visited the site and had constructive talks with the building contractors, T J Evers. We offered them a simple solution: to incorporate nestboxes made from clay airbrick liners inside the brickwork of the buildings, concealed behind slip bricks (a ~1 inch slice of brick) with an entrance cut in it, in most cases on the gable end. This is a low cost solution, and easy for the bricklayers to implement. [We have used clay airbrick liners on other projects here and here]

Example of a finished entrance

In this project, the exterior slip brick with its entrance slot is  mounted on the external face of the nest cavity. In this way, the provision of nesting accommodation is achieved without compromising either the fabric or the appearance of the building. 

Fourteen nestboxes were installed. Even in August and during the ongoing building work, workmen reported seeing birds entering some of the boxes. We know that one was a Great Tit, and the others were House Sparrows, but earlier, there was one report of a Swift seen in the vicinity of a box. We will need to monitor the situation closely next season, and if we can persuade one or two house owners to play attraction calls, there is a good chance of enticing Swifts.

Unfinished nest-box, showing the exposed
airbrick liner before covering with slip bricks

We learned something on this project: The size of the access hole to the nest cavity is critical. The recommended dimensions are Length 65-70mm, Height 30mm, but we know that at 30mm, Starlings can squeeze in, so we recommended a height of 28mm (tolerance 27mm-29mm). (Swifts will get into a hole as low as 25mm, but as they wriggle to get in, they may be vulnerable to predators).

In the event, there was some variation in the size of access holes, which is understandable. It suggests that in future, the boxes and their entrances should be pre-fabricated.

The building contractors were entirely enthusiastic and supportive, and it is to be hoped that they will take the message with them to future housing developments that they work on. We also hope that the message from Northumbria Close Haddenham will be heard by other developers across the land. It's the only way we can be sure that there will be Swifts in our skies in years to come.

The nest box entrance is barely visible in this gable end

Internal Swift nest boxes in a Belgian school

This project demonstrates a technique that has been used several times in the UK, but using commercial, off-the shelf products. Though possibly more expensive, the end result looks very professional. It uses identical products to this project. Whereas in this country, most projects have attempted to make the entrances 'invisible' (e.g. these four projects: 1, 2, 3 and 4), this project has some similarity to the very successful project in Fulbourn Cambs where the entrances were made conspicuous (5).
A heartening feature is the enthusiastic collaboration of the various stakeholders -  municipal officers, local councillors, building contractors and other interested parties. Without this kind of cooperative effort, schemes of this kind are very hard to bring to fruition. Well done, the town of Jette.

We thank Martine Wauters for allowing us to translate and reblog the post on her blog. In her own words:

The school before work started

This is the realisation of a wonderful project: nest accommodation integrated into a school building

I am pleased to announce that a project that I have been dreaming about for the last 5 years has finally materialised: the installation of eight nestboxes for Swifts integrated aesthetically into the facade of a local school (French section and Dutch section) of my town in Jette (Brussels NW), as part of a renovation project.

And it is the kind of project that I like: the result of a successful collaboration with several groups and individuals: from the municipality, including two aldermen from different political parties and two officials from different departments); one building contractor and his team; and several national and international experts. My thanks to them all!

Components: a face-plate, a pipe and a nest box

In alphabetical order, the contributors to this project are:
Louis Philippe Arnhem (Leuven), Swift expert
Laurence Bottini (Municipality of Jette), Municipal Heritage Department, and responsible for the building site.
Christel Matthijs, Director Gemeentelijke Basisschool Vande Borne (Dutch section of the school complex)
Edward Mayer (Swift Conservation, UK), Swift expert (www.swift-­conservation.org)
Coralie Meeus (Municipality of Jette), Ecoconsultant

A view from the outside

Dick Newell (Action for Swifts, UK), Swift expert (http://actionforswifts.blogspot.co.uk)
Johnny Van Belle (Euronet company), Entrepreneur, and his team (www.euronet­vanbelle.be)
Sylvie Vanderhaegen, Director of the Jacques Brel School (French section)
Claire Vandevivere (Municipality of Jette), Environment
Bernard Van Nuffel (Municipality of Jette), Municipal Property Assets

They are pioneers in the Brussels region, and indeed in the whole of Francophone Belgium Let us hope their example will be followed by many other entrepreneurs, councillors, officials and individuals.

Abroad, experience has shown that this type of development is appreciated by Swifts, who prefer nest boxes affixed under ledges. Fingers crossed that Swifts will soon discover the five­-star hotel we have created for them.

A view from the inside

Inside view of 4 nest boxes

Outside view of 8 entrances

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More experiences of retrofitting internal Swift boxes

There are a number of examples on this blog of retrofitted nestboxes in a roof-space, behind a gable end (e.g. here, here and here). We had not ourselves done this by using a core drill to make a hole through the wall, so when the opportunity arose, we grabbed it with open arms.

[Postscript July 2015: a pair moved into the right most box and raised 2 chicks]

[Update 2017: although, disappointingly, no Swifts turned up in 2016, by which time there were 9 internal boxes waiting for them, in 2017 4 pairs turned up of which 3 attempted to breed. Only one chick fledged, probably a reflection of inexperienced young birds].

by Dick

Christina Day, of Haverhill, had been trying to attract Swifts to some Zeist nest boxes installed under the eaves on the north east side of her house. She attracted Swifts alright, but they only paid attention to the fascia board on her south east-facing gable end. Thus she felt that she needed more nest boxes on this gable end. She bought 4 woodcrete boxes and contacted AfS to install them. The situation is ideal, as the gable end faces out over open land.

The roof trusses next to the inside wall, restricted what one could do with the woodcrete boxes, so we ended up making 2 plywood boxes.

Having established a reference point by drilling a single hole through the wall through the mortar, we then judiciously chose 4 suitable verticle bonds to make an entrance. This was achieved by using an angle grinder on the outside to slice a quarter brick off the ends of 2 adjacent bricks and then a masonry drill to remove the rest of the material.

This was quite hard work.

A hole from the outside through the middle of the vertical bond provided a reference point for using the 107mm diamond core to drill through the inner wall of soft concrete blocks.

This was the easiest part of the job as the core drill went through the wall like a knife through butter - quite therapeutic!

As in the case of Judith Wakelam's boxes, we used an insert fashioned out of a 30mm airbrick liner to make the entrances on the outside. A 4 inch plastic pipe, butted against the outside wall, bridged the cavity to the inside.

It was more than a full day's work for 2 of us, but we were pleased with the end result.

It would be so much easier if it was standard practice to build boxes like this in at the time that the house is built

The following pictures illustrate the result:

4 entrances

View through the pipe to the outside entrance

4 entrances prior to fitting nest boxes

Bill Murrells finishing off the installation of 2 plywood and 2 woodcrete boxes.

Picture of a diamond core drill

#inserts
#Cambridge

Fulbourn Community Swift Survey 2014

The nest boxing project at the 'The Swifts' housing estate in Fulbourn, Cambs is probably the largest and most successful in the country. You can read background information in Fulbourn Community Swift Survey 2013 and Fulbourn Community Swift Survey 2012. This report brings things up to date for 2014.

Contributed by John Willis

This was another successful year for the Fulbourn Swifts Group – our fourth year of surveying in the village. Our main focus was again on surveying swifts around the new houses of The Swifts Development, which was approaching completion, but also we were able to do some monitoring of the small colony located at St Vigor’s Church including undertaking some point counts for the RSPB. 

It was a great summer for the swifts with a substantial increase in observed nest box use and in our estimated number of breeding pairs thanks to the continued popularity of the internal boxes.

We met on site at 'The Swifts' every Wednesday evening between 7 May and 27 August, and individuals made observations on many other evenings during the summer as well. With 23 people active in the survey we had an average of 8 observers each Wednesday. As in previous years, several local residents reported observations made from their own homes.

To raise awareness of swifts in the village ahead of the swift season we published articles in the Parish Council Newsletter and the Parish Magazine and we distributed a flyer to all homes on the Swifts Development.  At the end of May we organised a coffee morning and swift display at the Community Library where we had support from Action for Swifts – Judith Wakelam provided photographs and display material and Bob Humphrey brought nest boxes. Also we mounted displays at The Fulbourn Community Market and the Fulbourn Feast in June and a few new people were recruited to the group.

On the Swifts Development an estate of 1960s system built houses, which had become home to a large colony of swifts (72 breeding pairs in 2009), has been demolished and replaced by new homes with provision of swift nest boxes. 

John Willis with an internal nest box.
Photo © Rosemary Setchfield

The boxes are of two types; internal custom made wooden boxes incorporated in the house timber frames in gable ends (see design here), and external Schwegler 1MF double boxes fitted on gable ends in phase 1 and on front/rear elevations in phase 2. The photograph shows the structure of an internal box prior to incorporation into the timber frame of a house. The plastic pipe is cut flush with the external brick wall.

At the start of the swift season, work on the final part (Phase 2b) of the Development was well under way with a number of houses having been completed over the winter.  This added another 20 internal and 10 external nest boxes bringing the total on the site up to 159 internal and 98 external – it was quite a challenge for us to successfully monitor all of these!

Our first swifts of the season arrived a little later than usual on 5 May and during the month there were decent numbers flying overhead but with relatively small screaming parties. 

Activity increased significantly at the beginning of June with an influx of prospecting young birds and with the generally good weather there were spectacular flying displays with large screaming parties throughout June and July. Peak numbers of 70+ were seen on 23 July with low level screaming parties of up to 20 birds providing a wonderful spectacle. Numbers started to decline around 27 July and by the beginning of August there were no more than 20 birds flying overhead and with virtually no screaming parties.  We were aware of 8 nest boxes still being used in early August and one pair were feeding young right up to 1 September.

Swift leaving an internal nest box
Photo © Judith Wakelam

This year, swifts were observed using 102 out of 159 internal nest boxes, 8 out of 98 external nest boxes and 4 sites in the one remaining old block – 114 sites in total. This represents a substantial increase on the 80 sites observed in 2013.  We estimated that there were 78 potential breeding pairs – 72 in internal boxes, 4 in external boxes and 2 in the old block. The corresponding estimates of potential breeding pairs for 2013 and 2012 were 58 and 32, so it appears that the colony is making a rapid recovery following the demolition of the old nest sites.  With 36 other sites having been prospected during the summer there is optimism for further growth in the number of breeding pairs in 2015.

The increase in activity comes from the third phase of the development (2a), which was part completed for the summer of 2012 and which the birds first colonised in 2013.  This area includes a high concentration of internal boxes (76), which are mainly in groups of four located on gable ends of houses and 3 storey blocks of flats – birds were using boxes in both types of location. Table 1 shows the history of occupancy.

		2012	2013	2014
Internal boxes	Available	111	139	159
	Visited	40	66	102
	Occupied	26	51	72
	% occupied	23.42%	36.69%	45.28%
Schwegler 1MF	Available	46	88	98
	Visited	4	9	8
	Occupied	1	3	4
	% occupied	2.17%	3.41%	4.08%
Total	Available	157	227	257
	Visited	44	75	110
	Occupied	27	54	76
	% occupied	17.20%	23.79%	29.57%
Old buildings	Occupied	5	4	2
Grand total	Occupied	32	58	78

Table 1: Summary of nest box activity 2012 - 2014.

Encouraging positive trends.

The major preference was again for the internal boxes with just one additional breeding pair using the external Schwegler boxes this year.  We have previously noted the presence of starlings in some Schwegler boxes but we have not observed any direct interaction between starlings and swifts. During April we walked the site on a number of evenings to assess the use of the external boxes by starlings and we were surprised to find that the starling population appeared to be relatively low.  We saw birds using 15 of the 98 external boxes and 2 of the 159 internal boxes and we heard evidence of young in just 5 of the external boxes.  We observed starlings using all four of the external boxes in the photograph below, but there was no evidence of young present.  Subsequently swifts nested in both of the top boxes for the second season running.

Schwegler 1MF external boxes
Swifts nested in the top boxes

So it appears that starlings are having little impact on swift use of this type of box. At the same time we noted sparrows using at least 9 internal boxes – nearly all of these boxes were subsequently used by swifts.

The builders have now completed the last houses of the Swifts Development so for the 2015 swift season there will be another 20 nest boxes available and we will have the task of monitoring over 270 boxes!  We will continue with our publicity within the village to maintain awareness of the project and to ensure that we have good participation in the 2015 survey. If any Fulbourn residents reading this would be interested in putting up a nest box or taking part in the 2015 survey, then please contact us at fulbournforum@gmail.com. 

Neat internal nest boxes in Nijmegen

We thought it worth reblogging 3 pictures from Jochem Kühnen's website, as they show just how unobtrusive, simple and effective built in nest-boxes can be.  Swifts are already occupying these nest-boxes.

Facade with virtually invisible entrances

Jochem says:
"I suggested several suitable nest bricks to the architects, and they went for this one. They placed 40 in the project in total, 10 in the facade where a Swift went in last week. I'm very happy with this development, this is a very busy square in the middle of the city centre, so a nice place to show people Swifts. Who knows, one day I'll go and stand there with a table with info to show passers by!"

The entrances were made by simply cutting a piece out of a brick and then positioning the Schwegler nest-box behind it

Entrance close-up

Schwegler internal nestbox

A new house with 9 new Swift boxes

[Note a download containing many more pictures is available in the Downloads section on the right]

[Update July 2014: 2 of these internal boxes were occupied in this first year, one with a horizontal slot entrance through the brickwork and a second one in a vertical slot entrance]

Bob Tonks already has 4 occupied external Swift boxes on his present house in Milton. He has now built a new house in Histon with a number of internal nestboxes of various designs and entrance configurations. 

The ideas are simple, of low cost and minimal inconvenience to the builder.
The following pictures should be self explanatory, click any one to see them enlarged:

Entrance made by 2 simple cuts in one brick

The above entrance leads to a box fashioned out of an air brick liner embedded in the inner wall

Air brick liner with entrance

Although unconventional, this simple idea provides a vertical slot

The vertical slot leads to a marine plywood box embedded in the inner wall. This box has a perspex back.
Two of these plyswood boxes also have a horizontally oriented entrance

3 entrances in a gable end. All of the boxes behind these entrances are made of marine plywood and
are embedded in the inner wall.

4 neat entrances into the eaves

Eaves nestbox design

Eaves nestbox installed

Retrofitted Swift boxes in a gable end

These are the neatest and most professional retrofitted internal Swift boxes we have seen.

The pictures below tell their own story, but first, in his own words:

Update 2016: Following one pair occupying a box in 2015, 2 pairs bred in 2016 as well as 2 more occupied boxes!

Michael Osborne

9 neat entrances in a gable end
There are more pictures on the Read more button below

We hired the equipment - a diamond drill and 117mm dry core. All the holes were drilled from inside to out. The breakout on the outer brick face is minimal if you back the drill pressure off when nearly through. Main thing to make sure is that the drill being used has a clutch and not to use the hammer action as it damages the diamond tips of the core.

The core has a pilot bit in the centre. It's best to start the drilling off with the pilot in place then remove it once the core is started, otherwise it slows drilling down.

The entrance plates are made from 12mm exterior cement board and cut using a tile cutter blade in a standard Jigsaw. The entrance holes were cut out by drilling through with a masonry bit big enough to get the Jigsaw in to then cut out the shape. To try and avoid the birds confusing entrances, I made some of the holes semi-circle shapes. They're all 29mm by 75mm. The runways inside the tubes are made from the same material as the entrances, glued into place using Sticks Like All Weather Adhesive. 

All of the entrances and runways were sealed with a brick sealant called Stormdry prior to painting. The tubes and entrance plate assemblies were then sealed into the wall using an exterior sealant.

The pipe used is a standard 110mm (external diameter) soil pipe, available at most DIY stores.

To match the brickwork I bought a number of Sandtex tester pots and mixed them in situ on the ladder to match the surrounding bricks - adding sand to get the correct texture.

The boxes are made from 12mm marine ply and are all 450mm x 310mm internally. The internal height is 200mm apart from a few boxes which needed to be reduced in order to fit them into the space. 

All of the boxes are wrapped in insulation to try and reduce heat transfer from the loft which gets hot during the summer. The angled brackets which the boxes are screwed to the wall with are available from B&Q. I've then sealed around any gaps between the box and the wall with a gap filler. The hinged backs have an acrylic viewing panel in them which have slideable covers on the outside - just in case the loft light is turned on accidentally!

Experimental Swift brick

by Dick

In publicising this idea, it is in the spirit of encouraging people to do experiments, rather than an idea that should be rolled out extensively, not yet anyway. The idea came out of the success of the air brick liner Swift bricks at St Neots. 

Swift brick with 2 fostered Swifts. Photo Judith Wakelam

The air brick liner Swift brick has internal dimensions: width 175mm x length 200 x height 100mm.

It thus occupies a space of length 1 brick and height 2 courses of brick. We wondered about a brick of height 1 brick - would this be acceptable to Swifts?

So, we built some prototypes out of 5mm thick fibre cement board. These have internal dimensions: width 150mm x length 225mm x height 75mm.

Swift exploring a Swift brick. Photo Clarke Brunt

In 2013, we installed 6 of these on 3 houses, all of whom were playing attraction calls. We managed to get Swifts to enter 2 of the boxes at one site, and we had them clinging to the boxes at a second site.

For the experiments, we have not knocked bricks out of any walls yet, but we have installed them under eaves with a simple wooden harness.

The width of these boxes could extend across the cavity, which, in modern houses, may be as much as 100mm, allowing a box width of 200mm. Also the length could be extended to 1.5 bricks ~330mm long. This would fit well in a Flemish bond.

4 fostered Swift chicks in a Swift brick

If this idea works, it would be the easiest thing to retro-fit into a wall, and may provide least resistance in the housing trade to install many of them in new build. We feel it could be a game changer.

For anyone who would like to have a go at this, please get in touch.

Postscript 2016: 2 of the boxes on one house were occupied by Swifts! The other 4 boxes have been occupied by House Sparrows.

Internal boxes with entrances fashioned from an air brick liner

From many points of view, built in nest-boxes are to be preferred to those hung on the outside of a wall, particularly if placed high up in a gable end within a roof-space. The nestboxes are secure, out of the sun and rain, and they provide a minimum of visual impact to the building. Although very easy to incorporate while a building is being put up, it is also not that difficult to retrofit them, but it does require some level of building skill. We have documented 2 examples here and here. 

[Postscript July 2015: A pair has raised 2 chicks in the the right hand box. The pair in the external heat-proof box has again raised 2 chicks]

The original double-walled external nest box and entrances to 3 new internal nest boxes

Model 400 air brick liner 220 x 200 x 65mm

Here is another idea using entrances made out of an air brick liner - this time the model 400 on page 10 of this PDF. This air brick liner has a hole 30mm high.

We previously described the success of a single, heat-proof nest box on the outside of Judith Wakelam's bungalow in Worlington. As Judith wished to have more nest boxes we decided to build 3 nestboxes inside the attic, rather than add more outside on this south-facing gable end.

Entrance fabrication

The air brick was cut up with an angle grinder, then the 3 component pieces were glued together with a resin glue, suitable for stonework. One can get at least 4 entrances out of 1 air brick liner.

A hole was made in the outer wall by removing 50mm from each side of a vertical bond in the brickwork, leaving a space big enough for half a brick - the size of the entrance piece. This can be done very neatly by drilling a hole through the mortar then using a sabre saw to cut the brick.

Bill Murrells installing the entrances. Photo Judith Wakelam

In this case, the inner wall was made of concrete blocks, so we chose to replace the height of a block with a nest-box, abutted against the outer wall with a waterproof membrane between the box and the wall. Alternatively, we could have used a 100mm core drill to make a hole in the inner wall providing access through a 100mm pipe to the nest box which would be hung on the inner wall.

Bill finishing off the installation. Photo Judith Wakelam

The nest boxes were made of weather-proof plywood. The removable wooden backs conceal a perspex 'window' to provide direct viewing when any birds become established.

Each box was fitted with a soft fibre-board nest concave.



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