Biodiversity Action Plan for the National Cycle Network ... - Sustrans

12. Mitigation and enhancement measures for wildlife
12.1 Bridge and viaduct maintenance
12.1.1 Bridges and viaducts can support, or be associated with, a number of species that
are protected by law. Protected species include badgers, bats, reptiles, amphibians
and nesting birds. When bridges cross water, otters and water voles should also be
included on this list. Saxicolous flora (attached to masonry) and small mammals may
also occur. Any maintenance works on these structures should take account of these
species.
12.1.2 Bridges of particular importance to wildlife are older stone bridges with cracks and
crevices in the masonry or bridges which are ivy-covered. Surveys, particularly for
bats and nesting birds, should be undertaken before any maintenance work
commences. This applies especially to pointing which could trap bats and, possibly,
nesting birds inside the masonry of the bridge or viaduct. Bird boxes and ledges, and
bird and/or bat holes/crevices should be incorporated into bridge maintenance works
whenever possible. It is also important that, where the route incorporates bridges, the
continuity of the habitat is maintained. Where possible a methodology to incorporate
a strip of vegetation, including hedgerow plants, on the bridge deck should be
included. Where the route goes under a bridge, dispersal routes can be maintained
by placing log or rubble piles against the walls. Both of these methods will ensure
that the bridges do not act as barriers to movement.
12.2 Bat bricks
12.2.1 Bat bricks are specially designed bricks that are either hollow with an entrance into
this space, or have a series of slits in them to allow bats to pass through into a space
beyond. The bricks are used in place of standard bricks and provide bats with
roosting sites as they act as artificial cracks and crevices that would naturally occur.
These may be particularly useful in bridges and viaducts where potential sites may
have been lost due to re-pointing works. The bricks can be installed by carefully
removing an existing brick to allow access to the interior of the bridge as bats will
penetrate up to a metre into the rubble fill. If this is not possible, self-contained bat
bricks can be attached to the existing bricks.
12.3 Bat and bird boxes
12.3.1 Before bird and bat boxes are installed, consideration should be given to whether
they are appropriate. Boxes sited along paths may be prone to vandalism so should
only be installed in places where there are few or no other nesting and roosting
opportunities. Boxes need to be placed as high as possible on the trees (between 2-5
metres) to minimise the possibility of predation and vandalism.
12.3.2 Bird boxes need to be fixed facing between north and south east as this will avoid
strong sunlight and the wettest winds. The box should also tilt forward slightly to stop
rain entering.
Sustrans’ Biodiversity Action Plan for the National Cycle Network (December 2007)
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