House martins build mud nests under the eaves of buildings and return to them each year. Renovation of buildings during or before the breeding season routinely destroys nests, which is illegal under the Wildlife and Countryside Act 1981.
Destruction of nests with eggs or chicks causes immediate mortality of eggs and dependent chicks. Adult martins that return to find nests destroyed may re-nest, but nest construction takes weeks and late nests produce chicks with reduced survival rates. The pattern of renovation destroying returning migrants nests is a predictable and preventable welfare harm that occurs repeatedly across the breeding range.