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When birds are banned: architectural tactics for managing birds

by John Gelder
NBS Special Projects Manager

Pigeons, seagulls and starlings are scavengers that have made themselves at home in towns and cities. But that doesn’t mean they are always welcome. John Gelder investigates architectural tactics, some of which are dealt with in NBS work section N16 Bird and vermin control systems.

Reasons for discouraging pigeons, seagulls and starlings from roosting and nesting on our buildings include nuisance and distress to the public as a result of the large numbers of birds involved; and mess, disease and damage to buildings from droppings. These factors may comprise ‘public nuisance’ in law, as in the 2001 Railtrack case involving pigeon-proofing of the railway bridge over Balham High Street. On the other hand, starlings are red listed, and herring gulls are amber listed, being species in decline, and should be tolerated.

Roost inhibitors

The practice of using spikes goes back a long way in the UK, as we see from the Sandwich church wardens' accounts for 1444 (quoted in Salzman, 1952, p290):

‘for xxiij yryn pykys that were made for to sette up on the poynts of the crossis of the pynnacles of the stepyll for ravouns schuld not stond ther on to soyle the stepyll and goterie with bonys and other things.”

Modern spikes may be metal or plastic, and are formed in rows on flexible polycarbonate bases adhered to the substrate. They can be coloured to be inconspicuous, though seen from below they tend to be in silhouette. Quite a few may be needed – rows should be fixed 100 mm apart, the spikes on a row are about 50 mm apart, and spikes are 120-150 mm long – creating a veritable forest on a wide ledge. Trapped rubbish may render them ineffective as well as unsightly.

Steel sprung wires are a less-conspicuous alternative for parapets, sills and the like. They are fixed using stainless steel eyelets. Low voltage wires are another option, but prone to breakdown.

Netting is widely used, e.g. to keep birds off capitals and recessed sculpture, to stop them flying through open trusses, and to keep them out of air intakes. For pigeons, 50mm gauge is used. BS 5502-30:1992 recommends 12mm anti-bird mesh over ventilation openings. Netting may be polypropylene (coloured to be inconspicuous) or galvanized wire, fixed using stainless steel eyelets. Birds often find themselves trapped behind the netting or tangled in it, resulting in RSPCA callouts. Starlings are prevented from nesting in chimneys using the familiar wire mesh balloons.

Gel strips, sealed in a resinous coating, make ledges slippery and the birds uncomfortable, but they harden and need to be replaced regularly. This isn’t easy. Gels can also ooze out of the coating (if the coating is applied at all) and stick to birds’ feet and feathers, so they are not recommended by the RSPB or PICAS (Pigeon Control Advisory Service).

Excluding birds from areas with vehicular access can be achieved using suspended proofing strips of heavy-duty clear PVC.

Visuals

These are a modern version of the classic scarecrow effect. Examples include 30 m plastic strips imprinted with holograms of owls’ eyes, and large balloons with a raptor’s face. However, as a general legal rule, nesting birds must not be prevented from accessing their nest, scaring devices must not be used near the nests of Schedule one species, and deterred birds must have somewhere else to go.

Sounds

The Hirshhorn Museum in Washington USA uses taped bird alarm calls, playing continuously, to deter birds from using the sculpture garden and facade. Some alarm calls, e.g. gulls, are very noisy and so not suitable for residential areas. A range of sonic and ultrasonic repellers is available, some targeting specific species, e.g. geese. Many are not species specific and will deter all birds.

Designing out birds

Buildings can be designed to make roosting and nesting difficult, without having to resort to unsightly physical deterrents. Nooks and crannies are easily avoided. Ledges can be steeply pitched rather than near-horizontal, and shallow rather than deep. Trusses in areas with ready bird access could, with a little effort, be designed to be closed rather than open.

Alternative accommodation

Barring birds from your building simply makes them somebody else’s problem. Giving them alternative accommodation solves the problem for everyone.

Enticing birds off buildings, by giving them somewhere else to roost or nest, was an option practised in the redevelopment of the Baltic Flour Mill on the River Tyne at Gateshead, UK, as a centre for contemporary art. Hundreds of kittywakes used the façade of the empty building as a nesting site. When redevelopment began in 1998, the Kittywake Tower was erected at the site, and that summer had 100 birds nesting on it. In 2001 it was relocated half a mile downstream, to an area of closely mown amenity grassland (Saltmeadows), and within a few weeks 100 pairs of birds had moved to the tower in its new location. It is now a designated Local Nature Reserve.

Dovecotes or columbaria are a traditional form of accommodation in which the owners took the birds for food. Modern owners have other objectives. In July 2000, the London Borough of Barking & Dagenham opened a dovecote in Barking Park, with the expectation that it would take birds off the roofs of a neighbouring public convenience and houses. Kirklees Council has built a thirty-pair dovecote in Huddersfield town centre, with a view to pigeon management. Other dovecotes, with the same purpose, have been built by Malvern Hills District Council in Worcestershire, Heath Park Hospital in Cardiff, and Nottingham City Hospital. PICAS reckons that ‘The dovecote is the way forward for large scale pigeon control in the 21st century’, though dovecotes alone will not do the job.

Nest boxes are used as much to encourage particular species of birds to visit as to encourage them not to nest on the buildings. They can be made species-specific by adjusting size and position of openings, nest box location, and general size and shape of the box. Over 60 UK species are known to use nest boxes, including starlings, for whom nest boxes should be placed under eaves. Nest boxes may be free-standing, or attached to buildings or trees, and may be for single pairs or many pairs of birds. They substitute for the holes found in old trees, which are getting scarce. Over 2003/05, 25 nest boxes were erected along the Wear in Durham as the result of a collaboration between an architectural practice and a primary school, under the banner 'The best Birdbox in Britain'.

Conclusion

Designers clearly have a contribution to make to the control of birds.

Management solutions will also be needed. But there is more to managing birds than simply keeping them off your buildings. Making buildings bird-safe, and encouraging selected species through landscaping, are other aspects to which designers can contribute.

References

BS 5502-30:1992, Buildings and structures for agriculture – Code of practice for control of infestation, BSI.

Building Research Establishment, 1996, Digest 418: Bird, bee and plant damage to buildings, BRE, Watford, September.

Lindsey, S., 2001, ‘Railtrack’s feathers ruffled after paying pigeon-proofing costs’, the architects’ journal, 7 June.

Salzman, L.F., 1952, Building in England down to 1540: A documentary history, Oxford.

Written May 2003, updated July 2007

 

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