Most birds do not harm buildings but where they are present in large numbers they may cause problems. Droppings can be visually disfiguring and damage surfaces such as stonework. This page summarises the measures you can take to deter birds to reduce the problems.
Bird droppings contain high levels of uric and other acids, phosphates, ammonia, potassium, and chlorides. The acids can attack the chemistry of stone, particularly limestones, and lead to salts causing efflorescence and spalling. Inappropriate and unnecessarily aggressive cleaning materials used to remove accumulated droppings can also damage stonework and decorative details.
Old nests, dead birds and droppings can block gutters and downpipes. Droppings can also be smelly and are a health hazard. Large numbers of birds such as Canada geese and their droppings sometimes pose problems in parks and green spaces too.
It is important to note that any deterrent must not stop birds from accessing their active nests.
As well as physical deterrents, you also need to think about an integrated management strategy to reduce the number of problem birds such as feral pigeons in the area.
Licences for the control of wild birds
By law (the Wildlife and Countryside Act 1981), it is an offence to:
- Kill, injure or take any wild bird
- Take, damage or destroy the nest of any wild bird while that nest is in use
- Take or destroy an egg of any wild bird
However, under certain circumstances, a licence to control birds can be obtained. Defra and Natural England are responsible for licensing the control of wild birds.
Building owners and occupiers, or their authorised operator, can use ‘GL41: general licence to kill or take certain species of wild birds to preserve public health or public safety’ but only to control feral pigeons, Canada geese, jackdaws and Monk parakeets.
There is no application procedure but you must follow the statutory guidance. The Secretary of State can modify or revoke this licence at any time.
Class licence to control gulls
Herring gulls and lesser black-backed gulls are not included in the general licence because of their ‘low conservation status’. The breeding population of herring gulls has fallen by 60 per cent in recent decades; that of lesser black-backed gulls has declined by 48 per cent. Rather than killing gulls, Natural England promotes integrated management strategies that reduce opportunities for gulls to nest and scavenge in problem areas within the built environment.
However, if necessary, Natural England can license gull control through an individual A08 class licence but you will need to make a good case that it is needed for human life and human health reasons.
Physical bird deterrents on buildings
Physical deterrents can be used to discourage birds from perching, roosting or nesting on buildings.
In keeping with the law, it is vital these measures do not trap, injure or kill birds, or interfere with other protected species such as bats that depend on historic buildings for roosts. Installation of deterrents must not take place whilst birds are nesting (generally February through to August).
If your building is listed or scheduled, you may need permission to install bird deterrents.
Your priority should be to try to bird proof the areas where birds sit and rest between feeding and flight, known as loafing areas, and previous nesting sites. You will also need to think about the service life and upkeep of deterrents. People will be rightly concerned and critical if they see trapped or dead birds.
Netting can be very effective and, if sensitively installed, is barely detectable. As netting is usually attached to stainless-steel wires or cables fixed to the building, you will need to think about the design to minimise damage to the facades. The size of mesh and the space between the fixings of the perimeter cables depend on the bird species. Fixings should be made into masonry joints rather than stone or brick work. In order to minimise the visual appearance of the netting on roofs, you will probably need to set the wires or cables back from the edge.
Netting comes in a range of colours so you can choose a shade that blends with the stonework or roof materials.
Care must be taken that birds cannot get trapped behind the netting.
Arrays of plastic or stainless steel spikes fixed along ledges can effectively prevent birds perching. However they can be visually obtrusive, and they may inadvertently create new nesting areas behind the arrays. You need to make sure that the plugs and screws used to fix them do not damage important features. They may also be fixed using silicone adhesive, or if installed in a gutter may be secured using cable ties.
These systems of fine stainless-steel wires are less obtrusive than spikes but may be less effective. The wires are tensioned by springs supported by stainless steel posts fixed at 1500mm centres to the tops of sills, cornices, parapets and other ledges. The posts are fixed by screws drilled into the masonry or with adhesive on metal flashing. Because the spacing of the posts is dictated by the need to tension the wires, there is little flexibility in where they can be positioned, which may result in fixings being drilled into masonry rather than mortar joints.
These require fewer fixings than spikes but are still visually intrusive and less versatile. Wire coils can be useful for deterring pigeons from perching on exposed ledges and parapets.
These systems are used to stop gulls landing and nesting on valley roofs. Parallel steel wires are installed horizontally at approximately 500 mm centres between the internal slopes of the roof. They are fixed each side to horizontal straining wires, running close to the roof slopes, which are fixed to the roof structure beneath the slates or tiles.
Using a caulking gun, tacky and repellent gels are applied to sills, parapets and ledges. These are specialist gels designed not to harm birds. The gels only have a short effective life span and will need regular replacement. As the gels and the sealant pre-treatments can harm porous masonry, and leave stains and residues, they are not recommended for most historic buildings.
Like electric fencing used to manage livestock, these wires can be used to deter birds. Fixings need to be carefully considered.
Other measures for controlling birds
As part of your integrated management strategy, you might want to consider other measures. You could contact your local council to see if there is a strategy or partnership in your area.
Control of litter
Control of litter is probably the most important action to deter birds. People should be encouraged not to feed gulls or feral pigeons, and you need to make sure birds can’t access food litter from bins.
Removing old nests and destroying eggs
The removal of unused nests outside of the nesting season is lawful and will prevent their re-use the following season. You are also permitted under the general licence to oil or destroy eggs.
Shooting, trapping and netting
Under the general licence, you can shoot or trap and take birds whilst not in flight with nets. Birds must be killed quickly and humanely. Canada geese are culled when they are moulting and cannot fly.
Model birds of prey can be used to scare off other birds. However, to be effective, the decoy needs to be regularly moved.
Using the general licence, some sites have employed falconers to use their hawks and falcons to scare off pigeons.
Reflective objects like CDs and scarecrows are often used to break the birds’ sight lines in gardens and allotments. However, these are unlikely to be suitable for historic buildings.
Bio-acoustic, sonic and ultrasonic devices
These devices make electronic noises to deter birds, but they may not work in urban settings and may not be accepted if they are audible to people. Devices must not be set so that they prevent birds from accessing active nests.
Ultrasonic devices must not be used in areas used by bats.
Where feral pigeon numbers are excessive and damage is being caused by their droppings, contraception may be an option to reduce their numbers. Electronic dispensers are used to feed the pigeons contraceptive-coated food pellets at set times in the morning when the birds are most active.
- Bath and North East Somerset Council - Urban Gull Strategy and Urban gulls: How to stop them nesting on your roof
- Gloucester City Council - Gulls: How to stop them nesting on your roof
- Newcastle City Council - Tyne Kittiwakes and the Use of Deterrents Guidance
Pest control contractors
The British Pest Control Association offers guidance on what to look for when searching for a pest control contractor. You should check contractors are fully and appropriately insured for the work, and technicians are trained and qualified to control pests safely, legally and effectively.
Health risks in work involving bird droppings
The Health and Safety Executive provides guidance on how to control the health risks in work involving bird droppings.