The house martin (Delichon urbicum) is a small, glossy blue-black and white hirundine that nests almost exclusively on the exterior of buildings — typically under the eaves. It arrives from sub-Saharan Africa in April/May and departs in September/October. Like swifts and swallows, house martins spend almost all their non-nesting time in the air, feeding on aerial insects.
House martins build cup-shaped nests from pellets of wet mud, collecting from puddles, pond edges, and bare ground. The availability of suitable mud is a critical welfare and breeding constraint.
House martin nests on buildings are frequently destroyed by householders concerned about nest droppings or mess, or lost to building renovation. This is illegal — active nests with eggs or chicks are protected. Destroying or damaging nests must wait until the nesting season is complete (typically November–February) and all birds have departed.
Drought years and the paving and sealing of soil surfaces in urban and suburban areas reduce mud availability. Nesting attempts in dry years may fail as birds cannot source sufficient mud to complete nests or repair damaged ones. Creating a mud puddle near nesting sites in dry conditions can be directly beneficial.
Like all aerial insectivores, house martins are affected by decline in flying insect populations. Cold, wet summers that ground insects cause chick starvation. Long-term food availability on breeding grounds and along migration routes is increasingly affected by climate change and land use intensification.
House martins undertake a substantial migration across the Sahara to winter in sub-Saharan Africa. The challenges of this journey — navigation, weather, predation, habitat degradation along the route — contribute to mortality. Climate-driven changes to rainfall patterns affect insect availability on both breeding and wintering grounds.
Specially designed artificial house martin nests (cup-shaped cups, available from wildlife suppliers) can be fixed under eaves to replace lost natural nests or attract new colonies:
In dry conditions, creating a wet mud patch near nesting sites can make the difference between successful and failed nesting attempts. A shallow tray of clay-rich soil kept moist provides the right texture.
Planting for insects (native wildflowers, avoiding pesticides), maintaining ponds, and reducing garden tidiness all support the insect prey base for house martins and other hirundines.