House martins have declined 57% since 1969, with nest site availability and aerial insect decline both contributing. Artificial nest cups installed under eaves can directly compensate for lost natural nest sites.
House martin welfare is affected by nest site availability and food supply. Modern buildings with smooth render and plastic soffits provide no attachment sites for natural mud nests. Owners who remove old nests or block nest sites directly cause breeding failure — a welfare harm and potentially an offence under the Wildlife and Countryside Act (all wild bird nests in use are protected). Artificial plastic nest cups, installed under eaves with a lip, are used by house martins within 1-3 seasons. Properties that maintain or install nest cups contribute directly to house martin breeding success and individual bird welfare.