Worthys Nature Watch


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Improving our Nature Habitats

Thistle (328KB) Slow Worms (468KB) Scarlet Elf Cup (648KB) Buzzard (240KB) Winnall Moors (460KB) Small Skipper (156KB)

Our key habitat project this year is conversion of an old WWII pillbox into a bat hibernacula ...

WWII Pillbox Conversion - Background & History

Numerous pillboxes in Kings Worthy and Headbourne Worthy are concentrated to the north of the area surrounding the army camp at Worthy Down.  During WWII this former RAF base (RAF Worthy Down) - built on the site of the old Winchester Racecourse - was handed over to the Royal Navy and became HMS Kestrel occupied by Fleet Fighter Squadrons 800 and 803.  In order to defend the camp from enemy attacks, and avoid the airfield’s capture, a blockade of defenses was erected circa 1940, including a perimeter of pillboxes.  Mostly Type 22, there are upwards of 30 pillboxes, situated in open fields, hidden amongst scrub in hedgerows and woods, semi-buried in the ground, a few in private gardens, and one even built around an oak tree (unfortunately now just a dead trunk!).

Since the war many pillboxes have been abandoned of no practical use in modern times.  An attempt was made to blow up one ‘inconveniently' placed, but this failed still clearly intact visible from Hook Pit Farm Lane.  Most are concrete appearance; however a few have an outer brick-shell.

Three pillboxes are accessible from Hook Pit Farm Lane; one on the lane itself (full of rubble) and two others (one brick) on the old DNS Railway line now a public footpath.  The pillbox identified for conversion is the southernmost of the two on the DNSR footpath, Grid ref SU 480 342, of concrete construction.

This section of the old DNS Railway line from Kings Worthy to South Wonston is owned by Hampshire County Council (HCC) Estates, from whom  permission for the work has been granted.  Worthys History Group having an interest in such historical artefacts has also been advised – indeed Worthys Conservation Volunteers had brought these WWII structures to the notice of Worthys History Group.

An opportunity by Worthys Conservation Volunteers to make use of an otherwise abandoned structure was identified.  And on discovering on the Internet that pillboxes elsewhere in the country had also been converted, members of the group set about researching into and campaigning for their potential as habitats for bats, culminating in the following scheme of work.

An added benefit of the scheme is the implicit protection in perpetuity of at least one of the pill-boxes.  It is the intention that any structural alteration shall be absolutely minimal, and that all works be reversible should the project prove unsuccessful.  Of course, once bats take up residence - which probably might take a few years - the roost is legally protected from all interference.

As well as HCC and Worthys History Group, support for the project has been given by a local bat conservationist who made a visit to the site in Spring 2010.


In masterminding the conversion certain criteria have been considered:

  • Must be cool and damp – bats need fairly constant atmosphere that is cool and damp, and rely on high-levels of humidity, so best if waterlogged at bottom.  The lower level entrance could act as a suitable sump for collecting water therein providing a means of maintaining dampness within the structure to provide a suitable roosting environment

  • Create suitable nooks and crannies – can be created between breeze blocks, using ventilation bricks.  Regular bat boxes probably offer the best option for resting-bats

  • Access from the side entrance is best – block all gun ports and leaving the entrance partly open for access by the bats.  Discourage access from the passer-by by limiting the size of the entrance although inspections will need to be made periodically.

The work will therefore entail:

1.  Blocking all the gun-holes (aka loopholes) with breeze blocks, fixed from the inside using a cement mortar.  Lightweight concrete blocks will be used having a much firmer constitution than although somewhat heavier.  A double skin of breeze blocks may be considered providing bats additional nooks or resting place between skins

This will have no real visual impact and is to be done so that no structural changes are made at all.  It would be possible to knock out the breeze at any time in the future should it be desirable

2.  Securing ready-made bat-boxes to the "Y" AR wall and also some onto the inner surface of the structure.  Any screw holes to be sited along mortar lines or in pre-existing screw holes if at all possible, so as to minimize structural damage

It has been noted that other conversion projects have used ‘holed’ bricks of varying types, however bat-boxes are considered the better option.  T

3.  Half-blocking the entrance, again with lightweight concrete breeze blocks, providing a suitable entrance-hole for the bats.  This is to deter children, dogs, etc, entering, and also to protect the bats from interference.  As inspections will need to be carried out every so often, access shall not be completely restricted but just made very difficult.  (Only licensed bat handlers will access the structure only once bats have moved in.)

Alternatively, a strong wooden frame mounted from inside and then a ‘door’ of double marine-ply or similar bolted with tamper-proof or key-operated bolts or screws from the outside would seem to fit the bill.

4.  Maintaining dampness within the structure by piping runoff rain-water into the entrance.

5.  Erecting an information board may be carried out – although this may encourage the wrong type of inquisitor.

6.  Monitor the presence of bats using suitable bat detectors.

Work Plan

The plan is to carry out the work over two tasks:

September 2010 - Block all gun-holes and fix bat boxes to walls


For blocking the gun-holes: 12 light-weight concrete blocks, cement, sand and water;

For the bat-boxes: ready-made bat boxes, gripfill, screws.


Wheelbarrow, spade, trowel, bolster, lump-hammer, cordless hammer-drill, torches.

October 2010 - Build entrance wall

Materials & equipment:

To be confirmed.

Dryads Saddle (428KB) Caterpillar (396KB) Water Rat nest (668KB) Orange Underwing moth (224KB) Wild poppy field, Headbourne Worthy (580KB) Common lizard (400KB)

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