House martins nest on the exterior of buildings and have declined significantly as building modernisation removes nest sites and reduces aerial insect prey.
House martins returning from sub-Saharan Africa to find their natal nest sites destroyed by building renovation face a welfare harm of displaced breeding. Birds that cannot find suitable nest sites cannot breed, representing a reproductive welfare failure after a 14,000km round migration. Building modernisation that removes mud nests without mitigation is a preventable welfare harm. Installation of artificial nest cups and preservation of existing mud nests costs homeowners nothing substantive.