The damage that bird fouling causes to historic buildings can be extensive. Apart from the obvious unsightliness, the main problem is acids released from their excrement. These can cause irreversible damage to building surfaces resulting in the scarring of building fabric, damaging appearance and, potentially, causing thousands of pounds worth of damage. Studies have shown that the corrosive effects can continue for a long time after the stone has been contaminated, even if the fouling is removed.
Pigeons are also known to pose a significant health risk to the public. There have been 176 documented transmissions of illness from feral pigeons to humans (Weber, 1979). Pigeons are known to harbour 60 different diseases, though only seven of these diseases can be transmitted to humans. Research has shown that aerosol transmission accounted for 99.4 per cent of incidences of disease transmission between pigeons and humans. The most commonly transmitted pathogens are Chlamydophila psittati and Cryptococcus neoformans. Pigeon droppings are known to transmit histoplasmosis, a disease which primarily affects the lungs. Histoplasmosis is caused by Histoplasma capsulatum, a fungus which grows in soil and material contaminated with bat or bird droppings.
About 99 per cent of the bird-control problems on buildings encountered by the authors of this article arise from the activities of just two species: feral pigeons (Columbia livia) and herring gulls (Larus argentatus). These birds fall into the general category of 'pest bird' species, all of which are listed on schedule 2 part 2 of the Wildlife & Countryside Act 1981, and they are therefore exempt from the protection offered by the Act.
