A small bird which is just 12cm in length, the house martin (Delichon urbicum) boasts blue-black upper parts and white under parts. It has a distinctive white rump which distinguishes it from the swallow together with a forked tail. These birds are mainly found in towns, villages and close to woodland. They are also be seen in areas of mixed agriculture or near water.
What is the House Martin’s distribution and population?
House martins are found across the UK but are rare in the far north and west of Scotland. Their UK population declined by a troublesome 47% between 1970 and 2014. There are currently 510, 000 breeding pairs in this country.
It is believed that climate change has impacted house martins as their survival rates are greatly influenced by the weather. They require rain in spring to create wet mud for their nests and then warm weather to promote healthy populations of insects. However, they do not fare well in periods of extreme weather and these have become more common in recent years.
Periods of bad weather during breeding and migration result in high mortality rates. Hot and dry weather also increases mortality as it causes dehydration and stress.
House martins have also been affected by the loss of suitable nesting sites due to barn conversions. Their overwintering sites in Africa have been degraded. This species now has amber status and is of conservation concern.
European house martins migrate south for the winter, mainly to Africa. Some birds have been found overwintering in Spain and Portugal.
What do House Martins eat?
Insects taken on the wing.
Where do house martins nest?
House martins originally built their nests on cliff faces. But by the 19th century, they had begun to make use of buildings. Cliff faces had been almost completely abandoned by the 20th century as the birds had adapted to living close to people. They now seek out sites in outer walls and under the eaves of buildings. House martins nest in colonies, typically with four or five nests, although larger colonies are sometimes seen.
Nests are constructed from pellets of mud mixed with grass and are lined with feathers and/or vegetable fibres. It takes up to two weeks to build the nest. Clutches feature four to five eggs which are incubated by both parents for 14-16 days. The chicks are fed by both parents and fledge after 22-23 days.
Did you know?
Breeding house martins were completely lost from London by the middle of the 20th-century due to air pollution. Later, cleaner air enabled them to recolonise the capital successfully.
House sparrows will often take over house martin nests, often ousting the house martins.