House martins build mud cup nests under the eaves of buildings and have declined by over 50% since the 1980s. Modern building designs and owner removal of nests contribute significantly to their decline.
Removal of nest cups destroys significant investment in nest construction and frequently kills dependent young. Owners who remove nests cause acute suffering to adults who return to find their home destroyed after a 5000km migration. Nestlings that fall from damaged nests require specialist rehabilitation and have low survival rates. The loss of traditional building styles removes nesting opportunities that house martins have used for centuries. Their dependence on mud from puddles and pond margins makes them vulnerable to drought during nest building.