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GIVING BATS A
GOOD INNINGS
EUROPEAN PROTECTED SPECIES WITH INTERNATIONAL
APPEAL
By Andrew Cowan N.D.Arb. November 2002
For
more info see: Arb
Assoc Guidance Note 1 (2nd Ed.)
Bats are perhaps one of
the most misunderstood and maligned of small mammals.
Possibly because we know so little about them,
our fear of the unknown, has lead to a wealth
of scare stories and fairytales that portray them
as evil and creepy. However, these unusual nocturnal
animals play many essential roles in our farming,
forestry and urban landscape. Their decline is
an indication of the sustainability of our countryside
as a whole, because bats flourish best where the
ecosystem is healthy and stable. Knowledge about
bats roosting behaviour has been limited to observations
made in and around residential dwellings. Where
they have been found hanging up in the attic,
flying around a barn or crawling out from under
roof tiles. As a result, some bats have been associated,
almost exclusively, with buildings, but this is
not their natural habitat. In this article Andrew
Cowan* explains the importance of trees and wooded
landscapes to these, essentially, arboreal species’.
Concluding with some background to the international
efforts that have been taken to protect bats in
Europe and how these have been transposed into
Acts and Regulations, within the United Kingdom
of Britain and Northern Ireland (UK), that have
a direct influence on arboricultural and forestry
management strategies.
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The
Brown long-eared bat (Pleotus auritus)
has a particularly quiet call and flies
very close to tree canopies. It is often
found roosting in the roofs of buildings,
but since it appears to take readily to
the use of bat boxes, it is thought to be
a common user of tree roost sites. Photograph
by John Altingham 2001 |
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THE IMPORTANCE OF ARBOREAL HABITAT
Bats are one of the most divers groups of mammals in
the world with over a thousand known species, but we
understand very little about them. They live in very
specific ecological niches, and as such are very vulnerable
to change. Trees and tree related habitats play a very
important part in the life cycles of nearly all bat
species.
The trees serve as sheltered habitat for the insects
on which the bats feed, while also acting as landmarks
and flight paths around the broader countryside. But
possibly one of the most important aspects is the use
of trees for roost sites. Bats are very depended on
having a divers range of roost sites. During the summer
some bats have been recorded using over thirty different
roost sites, sometimes only staining in one site for
one or two days. Even maternity colonies as a whole
are not averse to moving, with each mother carrying
her juvenile hanging from her nipple and fur to the
new roost location.
Bats use roosts for a range of different purposes for
such needs as overnight stops during summer feeding,
or gathering roosts in spring, to winter hibernation,
mating and breeding, and different conditions are required
for each. Roosts may contain few bats, or they may host
several species and many individuals.
A number of different research projects have shown
that on average an individual bat may spend 1.75 days
in one place, before changing roost sites. While the
average use of a single roost site by a colony of bats,
from the first individual resident, to the last bat
to leave, is 3-6 days.
Bats sometimes live more than twenty-five years, and
have been recorded at up to thirty years old. Once a
young bat has established a successful pattern of movement
and roost use, this will be repeated annually throughout
its life, with only minor deviations where roost sites
are lost. A sustainable and divers range of roost sites
can be instrumental in the continued viability of the
individual and local populations as a whole.
We know very little about bats, due mainly to their
nocturnal habits. Their movements through the landscape
are very difficult to record, despite modern radio tracking
techniques. Most of our knowledge is gained from recording
activities around known roost sites.
|
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| The Natterer's Bat (Myotis
nattereri), commonly associated with woodland
foraging areas, but most known roost sites
are in old timber frame or stone barns and
other farm buildings. This bat has a metal
identification ring attached to it's forearm
and is part of a long term research project,
monitoring population movements. Photograph
by John Altringham 2001 |
|
Research into bat
behaviour and habitat use has shown that at least
12 of the 16 species, breeding in the UK, use
tree roost sites, while 8 are known to do so regularly.
The species that have been found roosting in trees
are:
Barbastelle
Whiskered
Bechstein's
Brandt's
Daubenton's
Natterer’s
Leisler’s
Noctule
Common pipistrelle
Soprano pipistrelle
Brown long-eared
Grey long-eared
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(Barbastella barbastellus)
(Myotis mystacinus)
(Myotis bechsteinii)
(Myotis brandtii)
(Myotis daubentonii)
(Myotis nattereri)
(Nyctalus leisleri)
(Nyctalus noctula)
Pipistrellus pipistrellus
Pipistrellus pygmaeus
(Plecotus auritus)
(Plecotus austriacus) |
These species are generally distributed
throughout Britain with the exception of Bechstein's
bat and barbastelle, which are confined to central,
southern England and some parts of Wales. Several
species appear only rarely or as vagrants in Scotland,
but this may change as our climate gets warmer
and populations ranges shift and take advantage
of new opportunities.
|
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| The remaining
4 UK species may not have been found roosting in trees,
but there is a very high probability that they are using
them and there are simply no records of occupation of
such roost sites. These 4 species are:
Serotine
Nathusius’
Lesser Horseshoe
Greater Horseshoe |
Eptesicus serotinus
pipistrelle Pipistrellus nathusii
Rhinolophus ferrumequinum
Rhinolophus hipposideros |
It would not be unreasonable to say that all species
of bat use tree roost sites, to a greater or lesser
extent. In fact the use of manmade structures may simply
be due to the lack of suitable tree roost. Because tree
roosts are so difficult to locate it has always been
very hard to record the bats use of the sites and their
activities around them. This lack of accurate factual
knowledge has lead to a lot of misleading generalisation
and anecdotal information.
It is important to remember that each species of bat
has adapted a different way of utilising the available
habitat, and while there are some overlaps that result
in similarities, there are also things that are unique
to individuals, colonies and different species. A lack
of knowledge promotes a tendency to generalise and there
is a need to guard against the assumption that a conservation
measure designed to improve the habitat for one species
will be of benefit to all!
TREE FEATURES WHICH ARE USED BY BATS
Bats do not have the capacity to building nests or
excavate a roost site in a decaying trunk. However,
they are reliant on a divers range of appropriate places
to use as roosting sites from a few hours when using
it for feeding, to several weeks during hibernation.
An incredible variety of roost sites have been found,
from high rot holes at the ends of branches, down to
the cavities that are formed under buttress roots. Although,
one aspect of these sites appears to be similar, where
bats are found, they are squeezed into cracks and crevices,
or tucked out of the way behind loose bark or ivy. Bats
only very rarely hang free within a roost or out in
the open.
The nocturnal life style of bats enables them to take
advantage of a unique niche, allowing them to hunt insects
under the cover of darkness. However, finding a safe
roost site for the daylight hours is essential to avoid
predation. This can often be difficult, especially in
human dominated landscapes where natural habitats have
been extensively cleared, fragmented or modified. This
may be why some of the more adaptable species like the
pipestrelles and brown long-eared bats, frequently turn
up in roofs, while others like the greater and lesser
horseshoe bats have become dependent on the availability
of houses and barns for summer roost sites.
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| ROOST
SELECTION
Roost selection can be influenced by a number
of factors, not least of which is availability.
Competition for suitable cavities, splits, and
crevices can be fierce, with nesting birds, squirrels
and various mice species all looking for suitable
sites. This demand on what is very often a finite
resource can mean that bats are forced into less
desirable locations, while searching for sites
where they are less likely to be disturbed. This
may explain the use of what can sometimes be quite
precarious tree features like split branches and
behind loose bark.
Nothing is know for certain about how bats select
their roost sites, and we can only make educated
guesses made from observational research. For
instance, it was thought once that bats needed
a roost site that was at least 3m above ground
level, so when they took to flight there was enough
space for them to drop away from the exit point.
(A bat’s skeleton is very well adapted to
flight with a fine membrane stretched between
the thin bones of its legs, arms and fingers.
The drawback to this is that they do not have
the strength in their bones to support their own
weight, standing up, so cannot take off like a
bird.) However, more recent observations have
shown that bats can take to flight quite capably,
leaving a perch or roost site horizontally, and
often flying up.
Tree roost sites are difficult to identify and
are even harder to find without trapping and then
marking the bat with a fluorescent tag or attaching
a radio transmitter. By using such devices some
research projects have found tree roost sites,
and it has been possible to make some observational
comments on their use at different times of year.
Geoff Billington has radio tracked barbastelle
bats around Horner Woods on the National Trust
Holnicote Estate Somerset and some of the photographs
that accompany this article are of roost sites
which he has tracked bats to, in both winter and
summer.
In the summer female bats will group together
to form maternity colonies which tend to select
roost sites high in the tree canopy often at the
edge of a clearing. The young develop faster in
the warm conditions of a roost, which is in the
sun for much of the day. While the adult females
may choose to roost in a cooler place lower in
the tree canopy, returning to feed their infants
at night. Male bats have a more solitary life
style choosing roost sites in splits and crevices,
or behind ivy, and also tend to prefer colder
locations low in the tree canopy. |
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This
photograph shows the corner post of a timber
frame barn. At the top of the picture a
gap is visible on the under side of a mortice
and tennon joint, which Natterer’s
bats are using as a roost site. This species
of bat is commonly associated with old farm
buildings and is one of the species most
threatened by conversion of these buildings
to residential dwellings. Note the droppings
that have been court in the spider’s
web at the bottom of the picture. The presence
of droppings is often the only clue to the
location of a roost site. Photograph by
Andrew Cowan 2002 |
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Bats use torpor to conserve energy during periods when
insects may be in short supply, the reduction in body
temperature during inactivity greatly reduces metabolic
demands and thus the individuals’ food requirements.
Hibernation is a prolonged period of torpor which bats
use to survive though winter months. However, unlike
many other mammals that use torpor in this way, bats
will fly occasionally, to switch roosts or to snack
on winter flying moths, while taking the opportunity
to dispose of body wastes.
Knowledge about hibernation roosts is extremely limited
because bats are active for such a short period over
the winter months, trapping and tracking them is almost
impossible. While it has been know for a long time that
the Myotis spp. (many of which roost in trees during
the summer) make use of underground sites like caves
and disused mines. The other tree dwellers like noctule,
barbastelle, Leisler’s bat and both species of
pipistrelle, are only very rarely recorded and very
little is know about their habits.
Observations of bat hibernation sites, seams to indicate
that they prefer cool damp places with a stable temperature
around 1-6 degrees above freezing. So it has been assumed
that the bats hibernating in trees, use large cavities
deep in the trunk or at the base of the main stem. However,
Geoff Billington has managed to make some records during
his survey work at Horner Woods and his findings have
been quite surprising. He found two barbastelle bats
on different occasions behind loose bark not far from
ground level, while a group of noctule bats were found
hibernating at the top of a split limb, over 10 m up
an oak tree (see photographs). |
 |
| This impressive slit in
one of the major limbs of this oak tree has
been a maternity roost, used by barbastelle
bats, for several years, while a group of
noctule bats were found hibernating in the
top of the slit in November. Roost sites such
as this represent a considerable problem for
woodland managers, because they are valuable
habitat for bats, but where they are close
to areas with public access, there become
a significant health and safety risk. Photograph
taken at Horner woods, Summerset, by Andrew
Cowan (2002), where the property is owned
and managed by the National Trust, who have
commissioned some comprehensive bats survey
work undertaken by Geoff Billington of Greener
Ecology Consultancy. |
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TORPOR
Bats, like several groups of mammals in the
UK, have the ability to go into torpor. This
involves a complex sequence of regulated adjustments
controlled by the nervous system and stimulated
by hormones. During this process of body cooling
the heartbeat rate falls from a level of several
hundred beats per minute to an erratic figure
of around 5-20 in deep torpor.
During the winter hibernation period, torpor
can last for a few weeks at a time. Stored
body fat is gradually drawn upon to maintain
vital body functions. However, bats will also
use torpor to conserve energy during the summer
months, if a prolonged period of bad weather
reduces the availability of insect food, or
makes hunting difficult. |
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INTERNATIONAL CONVENTIONS,
DIRECTIVES AND AGREEMENTS
The precarious existence of bats is recognised
in Europe where they are protected under a number
of international Conventions, Directives and Agreements.
Individual countries have ratified these into
their national policy and legislation.
The Bonn Convention on the Conservation of Migratory
Species; arose in 1972 from a recommendation by
the United Nations, and entered into force in
November 1983. There are currently 79 parties
(as of 1st Feb 2002) to the Convention, which
include most countries in Europe. In addition
to the member of the European Union, many African
states and a growing presence in South America,
Asia and Oceania have also committed to the convention.
The United Kingdom ratified the Convention in
July 1985 and it entered into force on 1st October
1985.
The Bonn Convention aims to improve the status
of all threatened migratory species through national
action and international Agreements between range
states of particular groups of species. These
are covered by Articles II, III and IV. An Article
IV Agreement has been concluded as a self-standing
international legal instrument for the Conservation
of Bats in Europe. |
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The Berne Convention on the Conservation of European
Wildlife and Natural Habitats; was opened for signatures
in 1979, and was ratified by the United Kingdom in 1982.
Its principal aims are; -
• to ensure conservation and protection of all
wild plants and animal species;
• to increase co-operation between States in these
areas; and
• to afford special protection to the most vulnerable
of threatened species (including migratory species).
The Convention thus protects over 500 wild plants species
and more than 1000 wild animal species. It is open –
that is not limited to Europe – and is now in
force in 45 member states. It is the inspiration for
the EC Habitats and Wild Birds Directives and had a
direct influence on the UK’s main conservation
legislation, the Wildlife and Countryside Act 1981 (as
amended).
The European Community Directive on the Conservation
of Natural Habitats and of Wild Fauna and Flora 92/43/EEC
1992, identifies habitats and species of special interest
within the European Community, and legislates for the
notification of Special Areas of Conservation (SACs).
The Directive (92/43/EEC) requires Member States to
designate certain sites as SACs. From these national
lists, Member States and the Commission will agree the
Sites of Community Importance, which will become designated
SACs.
The UK has now forwarded 331 sites to Brussels as Sites
of Community Importance or Candidate Special Areas of
Conservation (cSACs). Together with Special Protection
Areas classified under the council Directive on the
conservation of wild birds (79/409/EEC), SACs will constitute
the European Union's Natura 2000 network.
The habitat types and species which require site designations
are listed in Annexes I and II of the Directive. Annex
III gives criteria for the selection of sites. 75 habitat
types and 40 species are proposed for site designation
in the UK. A document, ‘Selection of Special Areas
of Conservation in the UK', setting out in detail the
rationale for site selection was published by the Joint
Nature Conservation Committee in October 1997.
In all the above, bats benefit from their inclusion
within protected species list or where their habitat
is given special consideration. However, their importance
has been acknowledge specifically in The Agreement on
the Conservation of Bats in Europe (1994) known as EUROBAT
(www.eurobat.org). The Agreement was set up under The
Convention on the Conservation of Migratory Species
of Wild Animals, which recognises that endangered migratory-species
can only be properly protected if activities are carried
out over the entire migratory range of the species.
To date twenty-six European range states, from North,
South, East and West, are signatories to this Agreement.
The aims of the Bat Agreement are to protect all 37
species of bats identified in Europe, through legislation,
education, conservation measures and international co-operation
with Agreement members and with those who have not yet
joined.
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IMPLICATIONS FOR TREE WORK
IN THE UK
Bats also enjoy legal protection in the UK through
the Wildlife and Countryside Act 1981 (as amended),
the Wildlife (Northern Ireland) Order 1985 and on
the Isle of Man by the Wildlife Act 1990. Further
protection is provided by the Conservation (Natural
Habitats, &c.) Regulations 1994, the equivalents,
in Northern Ireland, is the Northern Ireland Regulations
1995, these are commonly referred to as the Habitats
Regs. In 2001 the Countryside and Rights of Way Act
2000 came into force, in England and Wales, and
included amendments to the Wildlife and Countryside
Act. These strengthen the protection for species
within the Schedules 1 & 5 of the Act, while
equivalent legislation is under consideration
in Scotland, at the time of writing no alternative
protection is available in Northern Ireland.
The UK Biodiversity Action Plan (UKBAP) published
in 1995, also includes targets and guidelines
for the protection of bats and their habitat,
while Local Authority Biodiversity Action Plans
(LABAPs) may also include locally important bat
species and habitat areas.
The introduction of the CRoW Act (Countryside
and Rights of Way Act 2000) last year, meant that;
considering the potential a tree has to contain
a bat roost, or form part of essential foraging
areas around a roost, has become an important
part of our pre-work job assessment. As professionals,
working in arboriculture, horticulture or forestry,
we could be seen as reckless if we did not consider
the potential and take appropriate action where necessary. |
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This
area of loose bark, which is less than 1.5
m above ground level, shows just how exposed
some of the tree roost sites can be. During
his radio tracking work around Hornor Woods,
Geoff Billington recorded a barbastelle
bat using this site as a hibernation roost.
Photographed by Andrew Cowan 2002 |
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FEEDING
TECHNIQUES AND FORAGING HABITATS
Navigation and finding
food in the dark are problems common to all bats.
Individual species have subtle variations in methodology
but the underlying theme is similar. All the British
species utilise echolocation for both navigation
and to capture prey. Some species add varying
degrees of eyesight to aid navigation whilst others
such as the long-eared bats use passive listening
to aid prey capture.
Echolocation techniques vary
between species depending on their favoured hunting
style and habitat. Only a small number of bats
are adapted to flight in open spaces, for the
remaining species a framework of landscape features
such as hedges, woodland edges and rivers are
essential to form flyways between the main foraging
areas.
At dusk or on moonlit nights
high hedges and woodland edges also provide some
protection from predators. While on dark nights
most bats will have less hesitation in crossing
big open fields, the shelter that hedges and woodland
provide also benefits the insects on which they
feed. |
|
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| A barbastelle bat was radio
tracked, in early winter, to this impressive
split in a low horizontal limb of an oak tree
in Hornor Woods, by Geoff Billington as part
of his survey work for the National Trust.
Photographed by Andrew Cowan 2002 |
|
A connective landscape, with high hedges and
tree lined waterways linking blocks of woodland
and unimproved grassland, is incredibly important
to the sustainability of any bat population. Where
a large road scheme, new bypass or carriageway
widening is likely to separate two or more forage
areas likely to be used by bats, this could have
potentially devastating results on the bat feeding
success
The Conservation (Natural Habitats, &c) Regulations
1994 (known as the Habitats Regulations), provided
protection not only for the bat and it’s
roost site (whether occupied or not), they also
cover the habitat used by bats both for roosting
and foraging. Where bats are concerned this also
included the flight lines they use between favoured
roost sites and good foraging areas. This becomes
an essential consideration when there is a proposal
to reduce or remove an old hedgerow, or where
clear felling sections of woodland is proposed.
The preservation of a connective landscape is
incredibly important.
Where bats are present in a tree, or if the tree
is a known roost, then consultation with the Statutory
Nature Conservation Organisation (SNCO) must be
undertaken prior to commencement of work. If bats
are disturbed during tree pruning or felling. then all work
must stop immediately and the SNCO contacted. The SNCO
will advice on the best action to take, including if,
how and when work can continue.
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Exemptions can be granted from the protection afforded
to bats under the Habitat Regulations, by means of a
EPS (European Protected Species) Habitats Regulations
licences. The Department for Environment, Food and Rural
Affairs (DEFRA) has the authority, in England, to provide
applicants with a licence for work that is likely to
affect a protected species.
Similar arrangements apply in Scotland where the Scottish
Natural Heritage (SNH) has a power to grant licenses
for scientific, educational or conservation purposes.
It cannot grant licenses for the purposes of protecting
public health and safety, allowing a development or
building project to proceed, or preventing agricultural
damage. In these cases the Scottish Executive is the
competent licensing authority |
In Wales the National Assembly for Wales (NAW)
has the responsibility for EPS Habitats Regulations
Licences, while in Northern Ireland they have
the Department of Environment (Northern Ireland)
(DoE NI).
A ‘EPS Habitats Regulations Licence’
could be required for;
- engineering work like bridge building or
repair,
- road building or widening
- woodland operations like thinning or clear
felling
- demolition of a building prior to development
of a site, residential or commercial
- tree felling during site clearance work
- tree pruning and felling in residential gardens
and parks
There are three tests, which must be satisfied,
before a licence can be issued to permit otherwise
prohibited acts;
- Regulation 44(2)(e) states that licences may
be granted to "preserve public health,
or public safety or other imperative reason
of overriding public interest including those
of a social or economic nature, and beneficial
consequences of primary importance for the environment"
- Regulation 44(3)(a) states that a licence
may not be granted unless the licensing authority
(e.g. DEFRA) is satisfied that "there is
no satisfactory alternative"
- Regulation 44(3)(b) states that a licence
cannot be issued unless the licensing authority
(e.g. DEFRA) is satisfied that the action proposed ‘will not be detrimental to the maintenance
of the population of the species concerned at
a favourable conservation status in their natural
range.’
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One
of the biggest and perhaps the most important
tasks that faces us now, is satisfying the
need for training, and the dissemination
of knowledge about bat behaviour. Geoff
Billington has established a successful
course for arboricultural and silvacultural
contractors and consultants (seen above),
based at Hornor Woods, in Somerset, while
the Bat Conservation Trust are working with
the Arboricultural Association to set up
an accredited training scheme for Arboricultural
Contractors. |
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All three
of test described above must be satisfied before a licence
can be granted by the licensing authority. If an application
for a licence is turned down this could mean that proceeding
with work on site, even where planning permission has
been granted, may be considered an offence.
Deciding when a EPS Licence is needed to carry out
work on a tree, or fell it completely, is not a straightforward
thing to do, and unfortunately there is currently no
official guidance. This issue will always stimulate
heated debate between, even the most experienced, ecologists
and conservationists. It is important to remember that
the legislation has been written to protect bats and
preserve their habitat, and not to prevent good tree
management.
INSPECTING TREES FOR BATS
With consideration to the number and diverse size of
tree features that bats could possibly make use of,
it is almost impossible to say whether or not a particular
tree(s) contains a bat roost. This represents a considerable
problem when considering tree pruning or felling work,
on what ever scale.
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BAT CENTRAL
At this road junction, just north of Horner
Somerset, there are a number of roost sites.
A Barbastelle (Barbasella barbasellus) was
radio tacked to a roost site in the old walnut
tree, while a Serotine (Eptesicus serotinus)
roost was discovered in the house opposite
and a Pipistrelle (Pipistrellus pipistrellus)
roost was found in the adjacent farm barn.
Photograph by Andrew Cowan 2002 |
|
It is therefore important that there is a procedure
in place that shows that the potential a tree
has to contain a bat roost (or whether it forms
part of a landscape feature used by bats) has
been considered at an early stage. This means
that the tree or trees should be assessed for
this potential as part of the initial site inspection.
It would be possible for instance to included
this with the site risk assessment.
Where a tree or group of trees may be thought
to have potential, then further advice should
be obtained from a private consultant or the local
SNCO.
If it is then considered that a EPS Habitats
Regulations Licence is required an application
will be needed to the licensing department (see
contact details below). A EPS Habitats Regulations
Licence will only be given to a suitably qualified
and licensed individual who will be acting on
behalf of the applicant as their consultant. The
appointed consultant will then be responsible
and will be expected to ensure that the terms
are complied with, in full, throughout the period
of the licence and where appropriate the monitoring
of any mitigation.
WHAT TO LOOK FOR?
An assessment of the potential a tree has to support
bats should form a routine element of all tree
surveys. Then, if certain features (listed below)
are identified, a closer inspection may need to
be considered, that could involve climbing the
tree to check potential roost sites, and the use
of a fibrescope to examine individual cavities
or splits. |
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Bats utilise trees for different purposes at different
times; it is important to be aware that untenanted roosts
enjoy legal protection.
Roosts may occur in the following features:
- frost cracks
- trunk and branch splits
- woodpecker holes
- rot holes where branches have been removed
- hollow sections of trunk, branches and roots
- beneath loose bark
- cavities beneath old root buttresses and coppice
stools
- in dense epicormic growth
- behind dense ivy
- in bat or bird boxes
Veteran trees typically exhibit many of these features
and should usually be regarded as sites with clear potential,
but any tree which possesses one or more such feature,
may host bats. |
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SIGNS OF ROOSTING BATS
MAY BE INDICATED BY:
staining around a feature (cavity or split) caused
by the natural oils in bat fur
scratch marks around a feature (cavity or split)
caused by bat claws, rarely visible
bat droppings beneath a hole (these resemble rodent
droppings but crumble to dust when rubbed between
finger and thumb)
urine stains below the entrance or end of split
audible squeaking from within the feature (cavity
or split), especially on hot days or at dusk
large roosts or regularly used sites may produce
an oder
flies around the entrance, attracted by the smell
of guano
Roost sites may be very small and not visible
from the ground and with no obvious signs of bats.
If in doubt contact the SNCO for advice.
TIMING, WHEN TO SURVEY
Visual inspections to assess the potential a tree
or group of trees has to provide roosting sites
can be completed at almost any time of year, although
it may be more difficult to spot all possible
features during the summer when trees are in leaf.
However, when a more detailed activity survey
is needed to establish how bats are using the
area and if possible identify which species, it
is important that this is done when they are likely
to be most active i.e. during the summer months. |
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Geoff
Billington can be seen here checking behind
some loose bark using and fibrescope. Geoff
has radio tracked a barbastelle bat to this
site, where it was recorded hibernating
over winter, even down to temperatures around
freezing, when there was frost on the ground.
Photograph by Andrew Cowan 2002 |
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Activity surveys can only be completed competently by
experienced bat workers or consultants with the appropriate
bat detection equipment and preferably with a scientific
licence from an SNCO. Although this type of work is
unlikely to be completed by the contractor or site manager,
it is important to be aware of the time constraints
involved and the influence of seasonal variations in
weather and how they affect the bat life cycle.
In large scale projects it is essential that adequate
time is allowed for a bat activity survey. What is involved
in such a survey will depend to a great extent on how
the site is likely to be affected by the proposed work
and how the bats are thought to use the area around
it.
OTHER BACKGROUND INFORMATION
If the survey involves contact with an owner or site
manager it is always useful to ask if bats have been
seen. The presence of signs, or reliable testimony,
necessitates consultation with the SNCO before any tree
work can be done. If no work is required then the potential
roost should be identified to the local bat group. It
is important that potential roosts are recorded within
an arboricultural database, and that roosts are made
known to all relevant organisations.
Local bat groups hold records of known roost sites
in their area and will provide this information (at
a charge) to interested individuals and organisations.
It is usual for the bat groups to confirm existence
of roosts within a certain radius of a site, but not
exact locations. However, this is generally sufficient
information to establish what activity is likely to
be recorded around a given area.
Aerial photographs can be useful to provide some overview
of an area and give a reasonable indication of potential
foraging areas and flight lines.
Tree survey: 3 steps
to good practice
1 - Is work required ?
2 - Are there signs of bats ? (Consult SNCO)
3 - Is there roost potential ? (Survey)
Government Departments – EPS Licensing Authorities
Department of Environment, Food and Rural Affairs, Licensing
Manager, DEFRA, European Wildlife Division, Room 1/08,
Temple Quay House, 2 The Square, Temple Quay, Bristol,
BS1 6EB. 0117-372-8291 Web site: www.defra.gov.uk
Scottish Executive Rural Affairs Department, The Scottish
Executive, Room 440, Pentland House, 47 Robbs Loan,
Edinburgh EH14 1TY. Tel: 0131 244 6023 Email: ceu@scotland.gov.uk
National Assembly for Wales (NAW), Cathays Park, Cardiff
CF10 3NQ. 029-2082-5111
Department of Environment, (Northern Ireland) - DoE-NI,
Environment and Heritage Service, Commonwelth House,
35 Castle Street, Belfast BT1 1GU. Tel 02890-251-477
Statutory Nature Conservation Organisations (SNCOs)
English Nature, Enquiry Service, Northminster House,
Peterborough PE1 1UA. Tel: 01733 455101. Email: enquiries@english-nature.org.uk
Website: www.english-nature.org.uk
Countryside Council for Wales, Plas Penrhos, Penrhos
Road, Bangor, Gwynedd LL57 2LQ. Tel: 01248 385732 Website:
www.ccw.gov.uk
Scottish Natural Heritage, Bonnington Bond, 2/5 Anderson
Place, Edinburgh EH6 5NP
Email: enquiries@snh.gov.uk
Website: www.snh.org.uk
Environment and Heritage Service (NI), Natural Heritage,
Commonwealth House, 35 Castle Street, Belfast BT1 1GU
Tel 02890-251-477 Fax 02890-546-660
Conservation organisation
The Bat Conservation Trust, 15 Cloisters House, 8 Battersea
Park Road, London SW8 4BG, Tel: 020 7627 2629, Email:
enquiries@bats.org.uk
Website: www.bats.org.uk
The Wildlife Trusts, The Kiln, Mather Road, Newark,
Nottinghamshire NG24 1WT. Tel: 01636 677711 Email: info@wildlife-trusts.cix.co.uk
Website: www.wildlifetrusts.org/
Arboricultural Association. 01794 368 717.
Ampfield House, Ampfield, Romsey, Hampshire SO51 9AZ
Geoff Billington, Greena Ecological Consultancy. Phone
01823 680450 Fax 01823 681429
Email geoff@npennines.fsnet.co.uk
Andrew Cowan N.D.Arb.
ArborEcolocy Ltd
37 Hartfield Crescent
West Wickham
Kent BR4 9DW
020-8462-7262
advice@arborecology.co.uk
* Andrew Cowan N.D.Arb. is Director of ArborEcology
Ltd. Having worked in Arboriculture since 1986, establishing
a contracting business in 1990 (Tree Craft Ltd), he
became licensed by English Nature in 2001 and now provides
advice on a range of issues relating to both bats and
trees. He is also author of the Arboricultural Associations
Guidance Note 1 – Trees and Bats, and provides
‘training’ and advice on a range of issues
relating to both trees and bats.
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