Effects of acid pigeon excreta on building conservation

Abstract

Purpose Birds are implicated in spoiling and decay of buildings, especially through their droppings. Pigeons are considered the main culprits, and several studies have examined the effects and chemistry of accumulations of droppings without evidence to the exact origins of the source of the excreta. The paper aims to discuss these issues. Design/methodology/approach This study reviews and summarises the state of knowledge with regard to the impact of bird excreta on buildings. It experimentally assesses the acidity of fresh pigeon excreta with different diets and examines the development of the acidity of the excreta after voiding. Findings Feral pigeons in urban settings are known to be fed by a range of foods. Urban food scraps-derived diets produce more acidic excreta than more natural diets such as seeds. This is a first study of its kind to examine the impact of a bird’s diet on the pH and thus the resulting (potential) decay of masonry. Research limitations/implications This study showed that from a management’s perspective, pigeons that subsist entirely on human provided foods will be depositing more initially acidic faeces. If faecal accumulation occurs; then, mould and other bacteria quickly alter the chemistry from acidic towards basic, but the damage may already be done. Originality/value This paper is the first study of its kind to examine the effects of fresh pigeon droppings of known origin and age once voided from the intestine. This allows the authors to assess the impact during the first few days.

Salt Weathering of 7th Century CE Granite Monument of Shore Temple, Mahabalipuram—Scientific Investigation and Conservation Strategy

“…On the upper part of the temple, bird droppings were observed. The weathering by bird droppings seems to be an active factor of the structural and textural changes, as well as the deterioration in some of the stones, as evidenced by various researchers [29][30][31][32]. A conservation mapping of Shore Temple that shows different types of deterioration and discoloration/deposits is shown in Figure 4.…”

“…various researchers [29][30][31][32]. A conservation mapping of Shore Temple that shows different types of deterioration and discoloration/deposits is shown in Figure 4.…”

Deterioration of stone and concrete exposed to bird excreta – Examination of the role of glyoxylic acid

“…In the case of existing buildings, measures to limit the 750 extent to which birds settle on buildings are well-established. Moreover, approaches to limiting the 751 acidity of pigeon excreta through controlling food sources that birds have access to have been proposed 752 (Spennemann et al 2017). 753…”

“…The deposition of bird excreta possesses the potential to initiate biodeterioration of the fabric of 44 buildings through a number of routes (Spennemann et al 2017). Mechanisms include the enlargement 45 of cracks and joints by vascular plants deriving from seeds in the excreta (Lisci et al 2003), and damage 46 from its chemical constituents.…”

“…After fungal growth, SEM examination of the marble surfaces found numerous 78 cavities and indentations in the surface, attributed in part to production of acid. 79 Slight acidification has also been observed during the growth of unidentified mould on pigeon excreta 80 (Spennemann et al 2017). The pH dropped from a value of 6.0 down to 5.4, over a period of 3 days, but 81 then increased over the next 8 days to a pH of 8.5.…”