Barn owls on site - working today for nature tomorrow - A guide for developers and planners
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Barn owls on site
A guide for developers and planners
working today
for nature tomorrow
2
Barn owls on site
A guide for developers and planners
Foreword
The archaeological record reveals that barn owls and man have been neighbours since
the Iron Age; this close relationship has survived right up to the present day. However,
over the last sixty years, changing land-use and agricultural intensification have
increased pressures on the barn owl. As a result, the barn owl population has shown a
dramatic and alarming fall.
Barn owls still make great use of old barns and other traditional agricultural buildings as
breeding and roosting sites. However, it is these refuges which are falling into disuse
and disrepair or being converted to homes, driving out the barn owls. Research has
shown that barn owl home ranges usually contain a number of roosting sites, but the loss
of just one may result in barn owls abandoning the entire area, rather than adopting a
new site.
The aim of this booklet is not to prevent the conversion or development of old barns but
to actively promote ways to encourage the co-existence of barn owls and man. This
booklet, aimed at planners and developers, is intended to provide all the most useful
information about barn owls and their housing needs.
On behalf of English Nature, I am delighted to welcome this positive approach by the
Barn Owl Trust. I recommend the booklet to all those with an interest in these owls.
If its guidance is followed, we can all look forward to the continuing co-existence of
barn owl and man.
Martin Doughty
Chair of English Nature
March 2002
3
4
Contents
Foreword 3
An introduction to the booklet 7
Background to barn owls 8
Barn owl identification 8
Feeding and habitat requirements 8
Breeding and roosting behaviour 8
Problems facing barn owls 9
Barn owl decline 9
The loss of prey-rich habitat 10
The loss of roosting and breeding sites 10
Other problems 10
Barn owls and the law 11
Legal protection and law enforcement 11
Licences 12
Interpretation of the law 12
Barn conversions and barn owls 13
Regional variation and the loss of sites 13
The effects of the loss of an occupied site on resident barn owls 14
The usefulness of making provision for barn owls 14
The importance of timing 14
The nesting period 15
Initial site survey 16
Search procedure and the identification of signs 16
Reading the signs 18
How to get help and who to notify 22
5
Planning for barn owls 23
Planning applications - outline stage 23
Planning applications - full applications and reserved matters stage 23
Protection prior to and during construction 26
What to do if eggs or young are discovered during construction 28
Protection after construction 29
Selling the site 32
Further reading 33
Appendices
Appendix A Indoor nestbox, specification and positioning details 34
Appendix B Provision for barn owls within a small loft area of a
converted barn or other dwelling 36
Appendix C Provision for barn owls within the large loft of a
dwelling or traditional agricultural building 36
Appendix D Example of an owl entrance hole through a hipped roof 39
Appendix E Age determination of wild barn owl pellets 40
Appendix F Useful contacts 42
Appendix G Barn Owl Trust recommendations for local and
national policy changes 44
Appendix H Quick reference guide 1 46
Appendix I Quick reference guide 2 47
Acknowledgements 49
6
An introduction to the booklet
The barn owl (Tyto alba) was considered Designed to present a positive approach to
to be very common during the 19th the development of occupied barn owl sites
century but has declined to such an extent and to provide planners and developers with
that it is now a rare bird over much of background information on barn owls and
Britain with some counties having only a the problems the birds face, the booklet will
few pairs left. As a result the barn owl is enable the reader to carry out an initial site
afforded special protection under the survey (to assess whether or not barn owls
Wildlife and Countryside Act 1981 (as are actually using a site) and to take
amended) and has as much legal appropriate steps to minimise the effect of
protection as any wild bird can have in the redevelopment on any birds which may
Britain. Individual birds, their eggs and be resident. The emphasis is on working
young are protected at all times and with and around barn owls rather than
nesting barn owls are protected against against them. The measures described are
disturbance. As nests are usually located all relatively inexpensive and are most
within buildings the implications for easily incorporated during conversion rather
developers are wide ranging. than added on afterwards.
The number of enquiries received by Barn conversion is one way of ensuring that
wildlife organisations and government part of our architectural heritage is
agencies has highlighted the need for a preserved. The Barn Owl Trust would like
publication to outline the implications of to see provision for barn owls incorporated
the legislation for development control into all rural barn conversions as a matter of
and the effects of site loss on barn owls. course whether or not birds are present at
the time of development. The simultaneous
During the 1990s the Barn Owl Trust conservation of old barns and their resident
carried out a major research project barn owls may be achieved with the help of
looking at the effects of barn conversions this booklet.
on barn owls. The effect of the loss of
occupied barn owl sites and the relative Readers who are new to the subject may
suitability of different types of alternative find it helpful to use the Quick reference
sites was investigated. This booklet was guides (Appendices H & I) Basic facts you
produced to facilitate the adoption of the should know and Frequently asked questions
recommendations contained within the (see pages 46 – 47).
Barn Conversion Research Project Report
(see Appendix G). This second edition
includes updates arising from the latest
research, new legislation, and new
recommendations based on best practice.
7
Background to barn owls season most foraging occurs within
about 1km of the nest. However,
Barn owl identification during the winter birds have been
recorded at up to 4.5 km from their
The barn owl is a very beautiful bird former nest sites. Food supply is the
with pale golden buff coloured upper- predominant factor governing barn
parts laced with silver grey and white owl survival and breeding success.
under-parts. It has a distinctive white
heart shaped face and when seen in The ideal habitat for barn owls is
flight the overall impression is of a rough grassland supporting a high
large white bird. Adult birds of both density of small mammals. This can
sexes are between 33-35cm from head be in the form of linear features such
to tail and have a wing span of as drainage ditches or woodland
approximately 85cm. Many people edge, or non-linear features such as
will recognise a barn owl from young tree plantations or fallow
pictures, but in the wild the species is pastures (see picture 13 on page 20).
generally very elusive. The birds are Intensively grazed pasture, silage
most active just after dusk and just and arable fields yield little prey and
before dawn, and as a result it is not the birds are not adapted to hunt
unusual to find that people living within woodland. Nevertheless,
close to an occupied site can be Barn Owl Trust studies have shown
unaware of the birds’ presence. that breeding barn owls are
Contrary to popular belief barn owls sometimes found with less than one
are not woodland birds and do not acre of rough grassland within 1km
hoot. They do however have a of the nest. Thus even in areas of
considerable vocabulary of calls intensive grazing and cultivation the
including screeches, hisses and possible presence of resident barn
snoring sounds. owls cannot be discounted.
Feeding and habitat Breeding and roosting
requirements behaviour
In Britain the field vole (Microtus Barn owls are often found in close
agrestis) is the barn owl’s main prey proximity to man, making use of
species; shrews and mice are also farm buildings, dovecotes, church
significant. During an average year a towers, bale stacks and a wide
breeding pair of barn owls and their variety of derelict and unused
young may consume as many as 5,000 buildings, as well as hollow trees
small mammals. In the breeding and cliff sites where available.
8
Site use falls into three main likely to survive and are likely to
categories: roosting and breeding, produce more young.
roosting only, or visiting occasionally.
Barn owls have been found breeding
Occupied sites are usually free from in all months of the year, but most
direct or unusual disturbance, that is eggs are laid in April and May. The
they are undisturbed or provide eggs are white, (see picture 10 on
opportunities for the birds to remain page 28) and are laid at about 2.5 day
unseen. The idea that barn owls intervals. The female begins to
require a remote site without human incubate as soon as the first egg is
activity is a myth; providing the birds laid. With a mean clutch size of 5.8,
have somewhere to hide, such as in a an incubation period of 31 days and
nestbox, they can learn to tolerate an average fledging age of 62.5 days
regular noises. Breeding sites must (9 weeks), it can be calculated that
have a large cavity or wide ledge as nests are occupied by eggs or young
barn owls do not build a nest but for an average duration of 108 days
require a level surface on which to lay (3.5 months). Fledged young often
eggs. Modern farm buildings are not return to the nest but have normally
generally suitable as breeding sites moved on by their 14th week. Second
unless nestboxes are provided. (and very rarely) even third broods
may occur.
A pair of barn owls will normally use
several sites in their home range, for
example a breeding site, several Problems facing barn owls
roosting sites and other sites that they
visit occasionally. However, some Barn owl decline
pairs seem to use their breeding site as
their only roosting place all year round. There is no doubt that Britain’s barn
owl population has suffered a severe
Once established, adult barn owls decline, although the evidence for this
show an incredible amount of site is largely anecdotal. Owing to its
fidelity – they usually remain faithful lifestyle, the barn owl is not an easy
to their sites from one year to the species to survey and as a result the
next. There is a growing body of national population can only be
evidence to suggest that the sedentary estimated. The comparison of various
behaviour and site fidelity shown by estimates would seem to indicate a
established adult barn owls has decline of approximately 70% since
survival value. Birds which know the 1930s. Although still widely
their home ranges intimately are more distributed over much of Britain, the
9
species population density is disappeared as a result of decay,
considered to be critically low over a Dutch elm disease, hedgerow loss and
great deal of its range. the general tidying-up of the
countryside. Modern barns are more
The loss of prey-rich habitat numerous than old barns, but are
generally unsuitable for the birds as
Intensive farming methods have they lack dark cavities for roosting
resulted in the loss of good foraging and breeding.
areas (particularly rough grassland)
through increased arable farming and In areas with numerous potential barn
intensive grassland management. owl sites, one would expect that the
Although arable farming and areas of loss of an occupied site would have a
short-cropped grass may provide some minimal affect on the resident(s) who
food for barn owls, it is generally would simply move to another nearby
considered that such impoverished site. However, research by the Barn
habitats are unlikely to support birds Owl Trust has shown that in many
during the winter or enable breeding cases the birds are reluctant to move
to take place. Winter survival in barn in this way. Furthermore, other
owls is closely linked to food occupied sites may be abandoned
availability and the first year survival when one site is lost and the birds
rate is only 25%. Food availability may disappear entirely from the
also exerts a powerful influence over locality. Adults which move away
breeding success. On average from their familiar home range are
breeding barn owls manage to fledge much less likely to survive.
just 2.6 young per year.
Other problems
The loss of roosting and
breeding sites Apart from the loss of habitat and
sites there are other problems which
Old barns used by barn owls are barn owls may face during their lives
disappearing from the countryside as (which are frequently very short).
a result of demolition and decay. The Periods of prolonged rain or snow
conversion of barns and the cover can reduce food availability.
redevelopment of derelict cottages has Road deaths account for 50-60% of
contributed to site loss as it is still known barn owl mortality. Drowning
unusual for any provision for barn in water troughs is not uncommon.
owls to be incorporated. Hollow trees Barn owls are frequently exposed to
are also used by barn owls, but secondary poisoning by eating
unfortunately these have also poisoned rodents. Barn Owl Trust
10leaflet No. 21 Rodent Control has It is not an offence to:
more information on these topics.
● Take (handle) a disabled wild barn
owl (unless you unlawfully
Barn owls and the law disabled it) solely for the purpose
of tending it until fully recovered
Legal protection and law and then returning it to the wild.
enforcement
● Kill, injure, take or disturb barn
All birds, their nests and eggs are owls if these were the incidental
protected by law under Part 1 of the result of a lawful operation and
Wildlife and Countryside Act 1981 (as could not reasonably have been
amended). Barn owls are listed on avoided.
Schedule 1 which gives them special
protection. Should anyone disturb a barn owl (at
or near the nest) who is genuinely
It is an offence, with certain unaware of the bird’s presence, this
exceptions, to: does not constitute an offence unless
it can be shown that the defendant was
● Intentionally kill, injure, or take reckless. Disturbance may be deemed
(handle) any wild barn owl. reckless if it is committed by someone
● Intentionally take, damage or who could be expected to know that
destroy any wild barn owl nest the bird(s) might be present but failed
whilst in use or being ‘built’ (barn to check.
owls do not ‘build’ a nest but may
make a nest scrape). Under the 1981 Act (Part 1, section
● Intentionally take or destroy a wild 25) local authorities are given the
barn owl egg. function of bringing this legislation to
● Have in one’s possession or control the attention of the public and may
a wild barn owl (dead or alive), or institute proceedings for any offence
egg, (unless one can show that it committed within their area. The
was obtained legally). police are empowered to enter onto
● Intentionally or recklessly disturb any land and search, or stop and
any wild barn owl whilst ‘building’ search, any person where an offence is
a nest or whilst in, on, or near a suspected (section 14).
nest containing eggs or young. Anyone found guilty of an offence is
● Intentionally or recklessly disturb liable to a fine of up to £5,000 or to
any dependent young of wild barn imprisonment for a term not
owls. exceeding six months, or both.
11Licences building as an occupied nest may not
be disturbing to the birds. Conversely,
The Country Agencies, English any unexpected prolonged and/or
Nature, Scottish Natural Heritage and noisy work within the building or
the Countryside Council for Wales close by may be extremely disturbing
can grant licences to permit otherwise to the birds and pose a major threat to
illegal acts. Licences may be granted breeding success.
for science, research or education,
conservation, ringing and marking or The bird’s sensitivity to disturbance
photography. varies a great deal. From pre egg-
laying until the brood average three
Licences can not be issued for weeks old the adult pair are likely to
removal of barn owls in order to be on-site and highly sensitive at all
facilitate development. times. From the time the brood is
three to four weeks old it is probable
Interpretation of the law that the adults will be roosting off-site
during the day and will not start food
It is important to note that barn owls deliveries until shortly before dusk. At
are only protected against disturbance this late stage in the nesting cycle it is
whilst at or near a nest containing sometimes possible for building work
eggs or young. ‘Near’ a nest is open to to be carried out during the day
interpretation but normally providing it has finished and everyone
approximates to within the same has gone home well before dusk. Nest
building or just outside*. In the case inspections can only be carried out by
of a tree nest circa. 30 metres*. a licence holder.
Breeding can occur at any time of
year and a site can only be proved not Professionals involved in the building
to be a current nest site through a industry (especially barn conversions)
detailed search being carried out (by a must be aware of the protection
licence holder). afforded to barn owls. It is reasonable
to expect such people to be aware of
* this does not constitute a legal definition the possible presence of protected
species in potential development sites.
Just what constitutes ‘disturbance’ is Therefore a professional who fails to
also open to interpretation. Generally assess the barn owl status of any
what disturbs barn owls is the probable barn owl site and then
unexpected. Thus, normal, frequent carries out a potentially disturbing
and regular human, animal or activity may be deemed ‘reckless’ and
machinery activity within the same thereby guilty of an offence.
12Barn conversions and barn The effects of the loss of an
owls occupied site on resident barn
owls
Regional variation and the loss
of sites The extent to which the loss of a
single occupied barn owl site may
Traditional agricultural buildings affect the resident bird(s) is likely to
provide the majority of potential barn depend to a large extent on the
owl sites and are used by the birds to availability of alternative sites within
a greater extent than other types of the birds’ home range. In areas with
site. There are however some regional few old barns, derelict cottages, or
variations within Britain. For large hollow trees it may be site
example, in south west Scotland availability which is the predominant
abandoned agricultural workers’ factor limiting the barn owl
cottages are important and in parts of population. In areas such as these
eastern England the majority of (south west Scotland, for example) the
known barn owl sites are hollow trees. loss of an occupied site may directly
In areas such as Devon the birds affect the overall population level.
depend on the availability of old barns However, over most of rural Britain
as there are very few derelict cottages there are potential roosting and
or hollow trees, and modern barns are breeding sites which are unoccupied
generally unsuitable. by barn owls and most old barns have
long since lost their resident birds.
The supply of traditional buildings is
finite and will eventually dwindle as Where site availability is relatively
conversion, demolition and decay high, one would expect to find that
continue to take their toll. Although the loss of one occupied site had little
barn conversion can ensure that some effect on the birds. However this is
traditional buildings are preserved, often not the case. In 1995 the Barn
(albeit in an altered state), where no Owl Trust’s Barn Conversion
provision for barn owls is made the Research Project provided the first
effect for the birds is the same as detailed information on this subject
demolition. Barn Owl Trust studies in and found that the loss of one
Devon have shown that in 1991, 10% occupied site can have a remarkable
of old barns had already been ‘knock-on’ effect. It is usual for
converted, 4% were undergoing resident barn owls to occupy more
conversion, and 20% were in a state of than one site; typically two or three
terminal decay or had already roosting sites may be used within 1.5
collapsed. km of the breeding site. The project
13showed that when one occupied site units, provided that these needs are met
was lost, barn owls not only and food availability in the area is
disappeared from that site but also sufficient.
abandoned other sites simultaneously
and often entirely left the area (within There is a lack of information as to
1.5 km of the lost site), despite the exactly how barn owls select the sites
fact that apparently suitable alternative they will roost or breed in within their
sites were available within the area. home range. Occupied sites are
The likelihood of this occurring may presumably those deemed most
depend on the age or temperament of suitable by the birds. Hence, where
the individual birds concerned. suitable provision for the birds is
made allowing them to continue to
The usefulness of making occupy their chosen site, they may do
provision for barn owls so in spite of development pressures.
There is nothing new about the idea of The cost of incorporating provision
people sharing buildings with barn for barn owls during the development
owls - there is evidence that barn owls of a site is minimal and experience
were roosting in farm buildings as has shown that there are no significant
long ago as the Iron Age. health or nuisance implications
providing that provision is made
It is often thought that barn owls prefer according to the.appropriate
isolated sites where there is little human specifications
activity, but this is simply not the case.
Long before barn conversions became Barn owls are such beautiful birds
fashionable there were cases of barn that, should the site ever be marketed,
owls roosting and breeding in the attics the presence of resident barn owls can
of lived-in houses and cottages. Barn afford the vendor a special selling
owls residing in traditional farm feature with great public appeal.
buildings may tolerate the conversion of
their home into a human dwelling and The importance of timing
continue to occupy the site, provided
that suitable provision is made. Under the 1981 Wildlife and
Regular human activity can be tolerated Countryside Act, active barn owl nests
by wild barn owls, as long as the birds are afforded protection against
have a dark cavity, well above ground disturbance, as are breeding adults
level, in which they can safely roost out and dependent young whilst at or near
of sight. Barn owls can occupy modern the nest. As nests are often situated in
structures, including rural industrial hidden cavities within old buildings or
14trees, it is not uncommon for the the remaining building works being
presence of an occupied nest to remain completed directly below them.
undetected until development of the
site commences. Emergency Barn owls have the longest breeding
situations where eggs or nestling barn season of any owl species and active
owls are discovered when an old roof nests have been found in every month
is being removed are all too common. of the year, so a cautionary approach
Most of these ‘worst case scenarios’ is called for. In buildings where fresh
have arisen not because the nest was barn owl pellets are found it may be
impossible to locate beforehand, but wise to assume that the birds are
simply because no preliminary search breeding and that no works should be
for signs of occupation was carried undertaken until it is proved that they
out. are not. Some roosting sites may be
deemed to be roosting-only sites
As a general rule, development during because it is obvious that there is
the breeding season should be avoided nowhere where the birds could
where there is any evidence of possibly be nesting. If there are no
occupation by barn owls. In cases other potential barn owl sites within
where a roosting-only site is affected it circa. 500 metres it may be deemed
is entirely possible that the development that the resident bird is not breeding
may have a detrimental ‘knock-on’ or that its nest is far enough away that
effect if the barn owl concerned has a any disturbance would not constitute a
nest nearby. contravention of the 1981 Act. Where
potential breeding places are available
The nesting period must be avoided at within about 500 metres and evidence
development sites where a building (or of recent roosting is found between
tree) which is a known breeding site is March and August, it is best to
due for demolition or redevelopment. assume that the bird is probably
In approving an application, planners breeding nearby.
sometimes attach a condition which
restricts the timing of the The nesting period
commencement of works to avoid the
main nesting season (March to August) The nesting period is normally
and requires the provision for the owls considered to be from the time that the
to be completed by the end of the female makes a ‘scrape’ and lays the
following January. This gives ample first egg until the time when the last
time for the adults to move in and ‘dependent’ young stops returning to
settle prior to egg-laying. When this the nest site. This is the period during
occurs the birds can be very tolerant of which disturbance must be avoided.
15As previously stated, eggs can be laid Initial site survey
at any time of year. Normally,
however, the first egg is laid in April, Search procedure and the
May, or the first half of June. The identification of signs
average date of first egg laid is May
9. The length of the nesting period When you first visit a potential
depends upon the number of eggs development site in a rural area you
laid and the number of young reared. may notice signs of occupation by
The absolute minimum time in which barn owls. The first stage is to be
one newly laid egg could become a aware that this is a possibility. An
newly fledged barn owl is 87 days. initial site survey can be carried out
With an average clutch and brood quickly and easily during a routine
size the period from first egg laid to visit. Whilst inspecting the site look
last young fledged is 108 days. out for droppings, pellets, feathers and
However, to these time periods must nest debris. Remember to consider
be added a further period of your own safety when inspecting old
approximately 10 days, as newly buildings and trees.
fledged young habitually return to
the nest whilst they are still Droppings - wherever birds perch
dependent on the adults for food. At they are likely to deposit their
sites where one newly laid barn owl droppings. In dry locations barn owl
egg is discovered and the protection droppings may remain for many
of breeding barn owls has called a months. These appear as large white
temporary halt to the development, splashes on a hard surface or smaller
the delay will not normally exceed white patches on old hay or straw (see
four months in total. It is unusual to picture 11, page 28).
find young nestling barn owls after
the end of August unless the first During dry summer months droppings
clutch of eggs failed and a may accumulate on roofs, fence posts
replacement clutch was laid or the or below tree branches. Most barn owl
birds are double brooding (breeding droppings are found on the floors of
twice in one year). farm buildings directly below the roof
beams where the birds perch. The
In cases where development work droppings may run down the roof
awaits the completion of a breeding timbers and appear as white vertical
cycle, a nest inspection should be lines (see picture 4, page 20). Where
carried out by a barn owl licence birds have perched on walls similar
holder before work is resumed (see white lines may be noticed. The
Appendix F). presence of droppings does not
16necessarily indicate occupation by barn normally in the month of May whilst
owls as similar large white droppings they may be breeding. The largest
are produced by various bird species. and most noticeable feathers (wing
They are, however, a good initial feathers) are normally shed during the
indicator of possible occupation. months of May to October for females
and July to November for males.
Pellets - barn owls generally swallow Barn owl feathers are very distinctive
their prey whole and regurgitate the and can render reliable information on
indigestible parts in the form of a site occupancy (see picture 7,
pellet. Barn owl pellets, composed page 25).
mainly of hair and bone, often
accumulate in places where the bird Nest debris - barn owls do not carry
regularly roosts. Lots of different bird nesting materials and do not build a
species produce pellets, including nest. If nests made of sticks are found
tawny owls, little owls, crows and within a building or tree hollow,
even sparrows. However, barn owl jackdaws or stock doves are almost
pellets are quite easily distinguished certainly responsible. The minimum
and can be a reliable source of entrance hole size required for barn
information on site occupancy (see owls to gain access into a building or
picture 12, page 31). When fresh, tree is only 7cm x 7cm (or about 8 cm
barn owl pellets are moist, black and in diameter if round). Buildings
glossy and they vary from thumb nail where barn owls roost or breed are
size to whole thumb size (see picture usually over 3 metres high with the
5, page 21). They are often rounded nest located in the uppermost part on
at both ends, but not always. If they a ledge or in a cavity. Barn owls need
have landed on a hard surface the a level area on which to lay their eggs,
pellets can be very flat on one side or normally over 3 metres (and very
one end. The drying and rarely less than 2 metres) above
decomposition rate of pellets depends ground level. Typical nest places
on where they accumulate i.e. pellets within buildings are - top of wall (see
in a wet location can disappear pictures 1 and 2), between bales, wall
quickly, whereas pellets in dry places cavity, nestbox, dry water tank, loft or
may remain for several years and can attic floor, between stored items and
be aged quite easily (see picture 6, wall, inside a chimney. Barn owls
page 24, and Appendix E). will sometimes breed on top of old
stick nests. Nests in tree hollows are
Feathers - barn owls begin their first normally located within the main
moult (with the exception of nestling trunk above ground level. In very
‘fluff’) at about 11 months old, large trees hollow side branches may
17be used. When searching tree cavities Reading the signs
a torch and a small mirror is an
advantage. Trees within an area of Assuming that evidence has not been
very dense woodland are not likely to removed by the action of humans,
be used by barn owls. animals or the weather, in dry
locations the signs may be read as
Note: If the initial site survey is follows (see pictures 1,2,4,6,7,11 and
during the main breeding season of Appendix E):
March to August and there is any
evidence of recent barn owl The presence of large white droppings
occupation of the site, do not attempt means “Good, look harder”; the
to search any potential nest places. absence of large white droppings
Consult your local office of the means nothing. The presence of only
relevant country agency, English a few crumbling pellets means the site
Nature, Countryside Council for was probably used by a barn owl at
Wales, or Scottish Natural Heritage, least a year ago. The presence of
(see Appendix F). approximately twenty pellets with a
wide age range (from crumbling to
Outside the breeding season you may glossy black) means the site has been
wish to check potential nest places visited occasionally for at least the
yourself. Recently used nest places past year. The presence of over 100
will usually have a distinctive smell pellets with such an age range means
(noticeable only at close quarters) and the site has been used regularly over
may show small pieces of white fluff the past year, and so on.
which were shed by the nestlings.
Whereas even the smallest of feathers The presence of only one feather may
moulted by the adults will have a mean simply that one adult barn owl
quill, a nestling’s fluff (mesoptile visited the site once during the
down) is distinguished by the lack of a summer. Remember that the presence
quill. Both the smell and the fluff are of feathers is a strong indication of the
likely to have gone within a month of site being occupied during the
the nest being vacated. What remains summer (May to November) by an
is a layer of pellet debris (see pictures adult (possibly breeding) bird.
1 and 2). When searching a building
for possible holes and potential nest If you are searching during the winter
cavities, remember that some wall and find thirty pellets all about the
cavities are only accessible from the same age - all dry and dark grey but
outside of the building (see pictures 8 still solid - and a few feathers, you can
and 9). be reasonably sure that an adult barn
18Picture 1 Nestling barn owls (eldest four weeks) showing fresh black nest debris on top of
old cob wall in the month of June. David Ramsden
Picture 2 The same nest nine months later (March) showing the previous year’s nest debris
which is now grey and dry. David Ramsden
19Picture 13 Although rough grassland is the optimum habitat for barn owls, please note that
they are sometimes found in areas without any. David Ramsden
Picture 3 (Right) An occupied barn owl
nestbox in the roof beams of a traditional
farm building. David Ramsden
Picture 4 (Above) When checking a site
for possible occupation by barn owls, look
out for vertical white lines down roof
timbers and walls. David Ramsden
20Picture 5 Barn owl pellets showing a variation in size and shape. David Ramsden
21owl roosted at the site for perhaps a found, it is a good idea to inform
month during the previous summer. the local office of your country
If some of the large feathers are agency - English Nature, the
brown on one side of the quill with Countryside Council for Wales
black bars (female) and other similar (CCW) or Scottish Natural Heritage
sized feathers are very pale or (SNH). If it is thought that barn
entirely white (male), then it is likely owls breed at or near the site of the
that an adult pair have both been proposed development the local
roosting at the site. Therefore office of English Nature, CCW or
breeding within the site or SNH should definitely be informed.
somewhere nearby is likely. Feathers If an active nest is discovered and
lying about become dirty and moth the development has commenced or
eaten in appearance and may become is imminent they must be informed
covered in cobwebs, allowing some immediately (see Appendix F).
indication of whether they were
moulted during the current year or a If you require any further
previous year. Anyone with a liking information on nestboxes, making
for a little detective work could provision for barn owls, habitat or
become fascinated! any other barn owl conservation
matter, you can contact the Barn
Although droppings, pellets and Owl Trust who have a range of free
feathers can all render useful information leaflets available by post
information, the absence of such or fax (see Appendix F).
signs does not necessarily mean
that barn owls do not ever use For advice on bats or badgers
the site. contact your local office of English
Nature, CCW or SNH. For advice on
other wildlife issues contact the
How to get help and who to Conservation Officer of your County
notify Wildlife Trust (see Appendix F).
Sample pellets and/or feathers may There are various groups and
be posted to the Barn Owl Trust for individuals involved in barn owl
identification (free of charge). conservation, some with more
Remember to include your contact relevant experience than others. For
details. help in your own area contact the
Barn Owl Trust, RSPB or country
If, during an initial survey, some agency and ask them to recommend
evidence of barn owl occupation is someone.
22Where evidence of barn owls is Planning applications - full
found on site prior to a detailed application and reserved
planning application being matters stage
determined, the relevant local
planning authority should be Once outline permission has been
informed as soon as possible. obtained the practicalities of
designing a scheme to
accommodate both people and
Planning for barn owls barn owls can be addressed.
There is no reason why, with
Planning applications - outline adequate foresight, they cannot
stage exist alongside each other, even
under one roof. Having
When an application for outline determined which parts of the
planning permission is made, even proposed development site are
at this early stage, it is wise to used by barn owls, the detailed
inform the planning authority that application should incorporate the
barn owls are present on site or that following measures:
some evidence of occupation has
been found. The application should ● At the earliest possible stage,
be accompanied by a full provide nestboxes in other
supporting statement indicating nearby buildings (which are not
which part of the site is known to be due for development) following
used by barn owl(s) and outlining the advice in Appendix A.
your plans to accommodate the ● Time the building works so as
birds and minimise disturbance to to avoid the birds’ main nesting
them. This will indicate the co- season (March to August).
operation of the developer in ● Shortly before building works
protecting the birds and help to commence, undertake a final
avoid delays at a later stage. search of each structure (or
Nothing is worse for both sides than hollow tree) involved to ensure
a situation where outline plans are that no breeding is taking
approved, detailed plans approved, place.
works scheduled, and then the ● Position noisy static machinery
presence of barn owls is notified by away from any buildings or
a third party. Better by far to trees occupied by owls.
acknowledge the birds’ presence ● Prevent site workers from
from the outset and to work with gaining entry into occupied or
them rather than against them. potential barn owl sites (on or
23Picture 6 Barn owl pellets showing a variation in appearance according to age (range - one
day < thirty months). Note; these pellets were collected from dry locations, see Appendix E
David Ramsden
24Picture 7 Barn owl feathers showing variation in size and colour. The presence of freshly
moulted feathers is a good indication of site occupation during the summer (May - November).
Paul Airs
25near the site) which are not due for it is probable that evidence will also
development so as to provide be found in one or more of the
‘sanctuary’ areas for the birds. others. If possible one or more
● Incorporate provision for barn owls nestboxes should be provided in these
into the part(s) of the development structures which are then designated
site used by the birds following the ‘no-go’ areas. Where the occupied
advice provided by this booklet. site is a single isolated building (or
● Do not leave any steep-sided hollow tree due for felling) and there
containers of water uncovered on are no potential alternative sites
the site (to avoid the risk of barn nearby, outdoor nestboxes should be
owls drowning). provided in trees, on the outside of
● Position new tree plantings and buildings or even on poles (see Barn
overhead wires to allow a clear Owl Trust leaflet No. 4 Outdoor
flight path for barn owls to and Nestbox Design). Generally,
from the access hole(s) provided however, indoor boxes are easier to
for them. provide and may be preferred by the
● Where possible, landscape the site birds (see Appendix A).
to provide areas of rough grassland
as foraging areas for barn owls and Once boxes have been provided it is
to encourage other native flora and not a good idea to inspect them.
fauna. Birds which have only recently
occupied a site may be particularly
sensitive to disturbance. As a matter
Protection prior to and of course all unnecessary disturbance
during construction should be avoided. Never attempt to
physically move a barn owl or its nest
At the earliest possible stage (prior to contents (see Barn owls and the law
any building work commencing) page 11).
alternative roosting and breeding
places should be provided in the form The aim during this pre-development
of nestboxes (see Appendix A). These stage is simply to enhance the
are best placed in structures where suitability of alternative sites the
there is already some evidence of barn birds are already using and to ensure
owl occupation as it is normally far that alternative sites are available in
easier to retain birds at existing sites every case. This will help to
than to encourage them into new ones. maximise the chances of the resident
birds remaining within their home
Where evidence of barn owls is found range whilst the development takes
in one of a group of suitable buildings place.
26Established adult barn owls are Incorporating provision for barn owls
naturally inclined to remain at the in the redevelopment of an existing
same site throughout their lives and building should be done at the earliest
may readily adopt any nestboxes stage possible. For example, when an
provided. However where occupied old barn is being converted into a
sites are lost and no provision for the dwelling the roof is normally
birds is made, the effect can be replaced. This is an ideal time to
devastating. The birds may not only create a new entrance hole (if
leave the lost site but may necessary) for the birds through the
simultaneously abandon other sites end wall close to the apex. As soon as
they have been using within their the new roof is complete provision for
home range. the birds can be made by boarding off
Picture 8 When checking a site for Picture 9 This cavity (note the debris and
potential nest cavities don’t overlook the droppings) was accessible only from the
outside of the building. Note the white lines outside of the site and could easily have
on the wall to the right of the ladder. been missed during a survey.
David Ramsden David Ramsden
27Picture 10 Five newly laid (clean) barn
owls eggs showing size variation and one
hatched egg showing natural discoloration
which can occur during incubation.
Paul Airs Picture 11 Typical accumulation of
droppings, pellets and feathers on old hay
what will become part of the attic area beneath a well used roosting place. Note
(see Appendices B, C and D). Thus the variation in colouration of the three
the building is ready for the birds to wing feathers indicating probable
occupy before most of the conversion occupation by a pair of barn owls. The
work has taken place. presence of numerous feathers indicates
occupation during the summer and the
Experience has shown that in such pellets are fresh (black).
cases the birds may occupy the new David Ramsden
provision whilst the conversion is still
being done and the builders’ regular
activities are often tolerated. What to do if eggs or young
However, unexpected extra-noisy are discovered during a
work close to an active nest must be development
avoided. Therefore the stage at which
provision for the birds is made may be With the use of this booklet the chance
determined by the timing of any extra- of discovering an occupied nest should
noisy construction phases in relation be minimal. However, as barn owls
to the breeding season (March to sometimes nest in cavities which are
August). inaccessible to humans there is a
28chance that an active nest could such as the age of the nest contents
remain undetected until development etc. It is possible that certain works
of the site commences. Typical may have to wait until the last
situations in which such discoveries dependent young has stopped
may be made are: when old hay or returning to the nest.
straw bales are moved, or when roof
sections are removed or hollow trees If an incubating female barn owl has
felled. Upon discovery of a nest the been flushed from the nest and eggs
following steps should be taken: are discovered, the nest should be left
alone as it is likely that the bird will
● Stop work. return. Cases have been recorded
where eggs have been temporarily
● If possible quietly replace the abandoned for up to 24 hours and
object which had previously have subsequently hatched
covered the nest (the last roof successfully. Although the vast
section removed, for example). majority of barn owl eggs are white,
occasionally viable eggs are
● Inform the site foreman and warn discoloured. For example, eggs in a
workers to avoid additional rusty old water tank can appear
disturbance. orange! If in doubt take advice.
● Telephone the local office of the
relevant country agency (English Protection after construction
Nature, CCW, SNH) immediately
(see Useful Contacts Appendix F) Landscaping the site may provide an
and follow their instructions. opportunity for creating areas of
rough grassland to encourage voles
Normally the country agency will and shrews (the barn owl’s main prey
arrange for someone with a barn owl species). As barn owls normally
nest inspection licence to visit the site forage over an area of at least 3 sq
and will ask for work to be temporarily km, most development sites are not
suspended at least until this visit has likely to include much of the birds’
taken place. feeding area. However, within the
intensively farmed landscape which
Every effort is made to ensure that the covers most of Britain, small patches
development can continue in a way of rough grass can tip the balance in
which is consistent with the birds’ favour of the owls. The birds may
welfare and the law. The advice given concentrate their hunting on quite
will depend upon numerous factors, small patches of long grass and
29commute from one to the next fill large cavities with sticks to the
ignoring short grass or cultivated land. extent that the cavity becomes too
Thus the provision of even small areas small for barn owls to use. The
of rough grass can be beneficial to clearing out of boxes and maintenance
barn owls as well as wild flowers, inspections are best carried out
butterflies and other wildlife (see the between October and January when
Barn Owl Trust leaflet No. 1 Habitat breeding birds are least likely to be
Management.) encountered and a licence is not
normally required.
The creation of new woodlands can be
beneficial in the short term, as small If rats or mice are found to be a
mammal populations build up in the problem on site it may be necessary to
rough grass between the new use a rodenticide bait. In areas where
plantings. However, the barn owl is rats have not developed resistance to
not a woodland bird, therefore some first genertation rodenticides such as
benefit is lost as the trees grow. Warfarin then it is better to use these
When planning a new copse, allocate products rather than the more toxic
slightly more ground than is required second generation products. If it is
to ensure a strip of rough grass necessary to use any products
remains around the trees. This should containing Flucomafen, Brodifacoum,
be topped occasionally to prevent Bromadiolone, Difenacoum, or
scrub encroachment. Alphachloralose then follow the label
instructions carefully. New safer
Nestboxes for barn owls do not need rodenticides are currently under
much maintenance provided that they development. For further information
are correctly designed, positioned and consult the Barn Owl Trust’s leaflet
secured. Once erected, boxes should No. 21 Rodent Control which is
be left undisturbed, although a regularly updated.
situation may arise where an
inspection is desirable. The main It is not uncommon for barn owls to
reason for nestbox inspection is for be found dead from drowning in cattle
monitoring purposes by ornithologists troughs or water butts. Many cases
during the nesting period. This can involve breeding females during the
only be carried out by someone with summer months. All steep-sided
the appropriate licence and the site containers of water should be covered
owner’s permission. Another reason or should have a means of escape
to inspect boxes is to check for incorporated (see the Barn Owl Trust
occupation by other species. It is not leaflet No. 31 How to Prevent
unusual for instance, for jackdaws to Drowning for further information).
30Picture 12 Pellets produced by various bird species. Barn owl pellets are much darker than
tawny owl pellets which are normally grey and may show insect remains. Little owl pellets
often show insect remains (kestrel pellets are very similar). Jackdaw pellets are highly variable
in content. David Ramsden
31Selling the site The Barn Owl Trust has produced a
leaflet specifically for the owners of
Second only perhaps to the robin, occupied barn owl sites. Where
the barn owl is one of the best occupied sites are sold it is
known British birds and certainly suggested that such information is
one of the most attractive. Its decline provided to the new owners as a
and the conservation work matter of course (see leaflet No. 28
undertaken on its behalf has received Safeguarding Wild sites).
much publicity. As a result the barn
owl is admired by many people from
different walks of life. The presence
of these magnificent birds would
certainly be seen as a unique selling
point by a significant proportion of
home buyers who would welcome
the opportunity to live alongside
these beautiful owls. Wild barn owls
are easy to live with.
It is often surprising how much
human activity wild barn owls can
become accustomed to, provided
they can tuck themselves away in a
dark cavity high above the ground.
Regular domestic activity is not
likely to disturb the birds at all and
experience has shown that barn owls
can roost all year round and breed
annually in the roofs of occupied
dwellings with children playing,
dogs barking, cars coming and going
and bright outside lights.
There are of course a minority of
people who don’t like the idea of
having birds in their attic, but once
suitable advice has been given,
genuine problems are virtually
unheard of.
32Further Reading Bats in Houses
Hutson A. M.
Barn Owl Trust free information Available by post (cost £1.20 inc.
leaflets include: p&p) from
No. 1 Habitat Management The Bat Conservation Trust
No. 3 Indoor Nestboxes London Ecology Centre
No. 4 Outdoor Nestboxes 45 Shelton Street
No. 21 Rodent Control London
No. 22 Barn Conversions WC2H 9HJ
No. 26 Survey Techniques
No. 28 Safeguarding Wild Sites Bat Information Pack - for Architects
Please send a large SAE to and Surveyors
The Barn Owl Trust Free of charge from
Waterleat The Bat Conservation Trust
Ashburton London Ecology Centre
Devon 45 Shelton Street
TQ13 7HU London
Or visit the Trust’s website at WC2H 9HJ
www.barnowltrust.org.uk
Barn Conversion Research Project
Badgers on Site - A Guide for Report
Developers and Planners Ramsden D. J. (1995) Barn Owl Trust.
Cox, P. R. (1993) Available by post (cost £10 plus £2
ISBN 1851631682. p&p) from
Available by post (cost £3.00 inc. The Barn Owl Trust
p&p) from Waterleat
Babtie Public Services Division Ashburton
Shire Hall Devon
Shinfield Park TQ13 7HU
Reading
RG2 9XG The Barn Owl
Taylor, I. R. (1989)
Bats in roofs - a guide for surveyors Shire Publications
Available free of charge from ISBN 0-7478-0024-3.
English Nature
Northminster House
Peterborough
PE1 1UA
33Appendix A
Indoor nestbox, specification and positioning details
Construction opening will see the box entrance
Indoor nestboxes for dry locations are hole and have an easy flight path
often made using a packing case such as to it.
a tea-chest. Alternatively a purpose-built ● At least 3 metres above ground
box may be constructed using 9 mm level - normally at or near the
softwood ply (CDX) and batten as apex.
necessary. Boxes made of thin plywood ● Within a building where there is
are lightweight and therefore easier to some evidence of a barn owl
erect (see Figure 1 on page 35). roosting or visiting.
● Within a building which is not
The use of tropical hardwood is not subject to increased disturbance
sustainable and should be avoided. in the late winter or spring.
Always select Canadian or Scandinavian Avoid farm buildings used mainly
softwood ply. If a tea-chest is re-used, for lambing.
ensure that the foil lining and any sharp
nails or strips of metal that might injure Lining the box - although it is not
the owls are removed. necessary to put anything in the box
you may wish to provide a layer of
Note wood flakes. Do not use sawdust,
This design of box is only suitable for peat or hay.
use within buildings. For details of an
outdoor nestbox design please send The Barn Owl Trust’s leaflet No. 3
for a copy of Barn Owl Trust leaflet Indoor Nestboxes contains additional
No. 4 Outdoor Nestboxes. information on this subject.
Positioning
Wherever possible, indoor nestboxes
should be positioned as follows:
● Within a building with an owl
access hole at least 3 metres above
ground level.
● So that an owl entering the
building through the most likely
34Update (October 1999)
Following several years of trials the
Barn Owl Trust have changed their
recommended indoor nestbox design.
The new design reduces the chance of
nestlings falling out of the box. Lift-off lid fitted
loosely with
batterns on
underside
25cm 13cm
13cm
(10“) (5“) 60cm
(24“)
40cm
(16“)
50cm
(20“)
Figure 1 Indoor nestbox design
35Appendices B and C
Provision for barn owls within loft areas
See illustrations on pages 37 and 38. There are various factors to be
considered when deciding which part
There are numerous ways in which of the development to make provision
provision for barn owls can be in. It is very important to incorporate
incorporated into buildings. Where human access into the owls’ nesting
indoor boxes are provided in area as occasional maintenance may be
traditional agricultural buildings they needed. Wherever possible the owls’
are normally attached to the roof entrance hole should be positioned:
timbers as shown in Figure 3.
(illustration on page 38). As barn owls ● So as to allow the birds to enter the
seem to prefer an enclosed nesting building in the same way as they
cavity high above the ground the did prior to the development.
provision of a nestbox (see Appendix ● At least 3 metres above ground
A) can greatly enhance the suitability level.
of the site. In houses or barn ● Avoiding obstructions such as trees
conversions with a large loft, provision and overhead wires.
for the birds can be made in this way. ● Facing away from the prevailing
wind.
In buildings with only a small loft ● On the side of the site which will
where the space may be so small as to be the least disturbed, after the
make the provision of a nestbox completion of the development.
impractical, the birds will nest on the ● Overlooking open countryside and
floor as shown in Figure 2. visible to any passing birds.
(illustration overleaf). As the young
owls develop they will move around a Although not essential, it is a good idea
great deal before they can fly, for this to provide an external perch or landing
reason it is important to position the platform which will give emerging
entrance/exit hole at least 40 cm young owls more room to exercise their
above the level of the nest area to wings before their first flight.
prevent the nestlings falling out. An
adult barn owl needs a minimum of
40 cm headroom and the absolute
minimum floor area recommended is
40 x 40 cm.
36Human access
hatches
Hole slopes slightly
upwards to prevent
ingress of rainwater
barn or other dwelling
Landing ledge
37
(optional)
Boards covering
loft insulation
Entrance hole
minimum size
12cm wide x 25cm high
Additional loft (5” x 10”)
insulation (for
sound proofing)
Figure 2 Example of provision for barn owls within a small loft area of a converted
Loft insulationIndoor nestbox
Figure 3 Example of provision for barn owls within the large loft area of a dwelling or
position (see
Appendix A)
Landing ledge Human access
(optional) door
Hole slopes slightly
upwards to prevent
ingress of rainwater
38
traditional agricultural building
Entrance hole
minimum size
12cm wide x 25cm Additional loft
high (5” x 10”) Boards covering insulation around
loft insulation covered water
tank if necessary
Warning
Do not use material such as old carpet to
cover loft insulation as young barn owls can
become entangled in loose threadAppendix D
Example of an owl entrance hole through a hipped roof
It is possible to create an owl access
hole through the roof itself (see Figure
4). This is fairly simple during the
construction of a slate roof using
either a decorative mini-dormer style
construction or a ready-made welded-
lead ‘owl tile’ (please contact the
Trust for further details). A similar
hole can be created during thatching.
Figure 4 Example of an owl entrance hole through a hipped roof
39Appendix E
Age determination of wild barn owl pellets
(from dry locations)
Method and limitations The descriptions opposite can be used
as a guide to age determination
Method provided that the pellets in your
As part of the Barn Conversion sample:
Research Project a reference
collection of wild barn owl pellets was ● Are barn owl pellets.
established. When very fresh (wet) ● Have lain in a dry position since
barn owl pellets were found during regurgitation.
searches of dry roosting sites (usually ● Have lain undisturbed and
farm buildings) they were carefully uncovered.
removed. The samples were then ● Are not comprised of remains from
dated and placed in a dry outbuilding unusual food items such as birds
alongside other barn owl pellet (identifiable by the presence of
samples. All of the pellets in this feathers) or frogs (identifiable by
collection contained small mammal the absence of hair).
remains.
Pellet samples may be posted to the
Limitations Barn Owl Trust for free species
The drying and decomposition rate of confirmation and an estimate of age
pellets is likely to be variable and may where applicable. If you find a
depend on numerous factors e.g. time suspected owl pellet which is very
of year, presence or absence of clothes smelly it is not from an owl so please
moths, micro-climate of roosting site don’t post it to the Trust!
and the diet of the birds concerned.
However, despite these limitations, Barn owl pellets found in dry roosting
pellet age determination holds great sites may be compared to the
potential as a source of information descriptions opposite. (See picture 6,
on present and past site occupancy. page 24).
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