UKBirds

House Martin

Delichon urbicum

The Common House Martin (Delichon urbicum), sometimes called the Northern House Martin or, particularly in Europe, just House Martin, is a migratory passerine bird of the swallow family which breeds in Europe, north Africa and temperate Asia; and winters in sub-Saharan Africa and tropical Asia. It feeds on insects which are caught in flight, and it migrates to climates where flying insects are plentiful. It has a blue head and upperparts, white rump and pure white underparts, and is found in both open country and near human habitation. It is similar in appearance to the two other martin species of the Delichon genus, which are both endemic to eastern and southern Asia. It has two accepted subspecies.

Both the scientific and colloquial name of the bird are related to its use of man-made structures. It builds a closed cup nest from mud pellets under eaves or similar locations on buildings usually in colonies, but sometimes fouling below nests can be a problem.

It is hunted by the Eurasian Hobby (Falco subbuteo), and like other birds is affected by internal parasites and external fleas and mites, but its large range and population mean that it is not threatened globally. Its proximity to man is generally accepted leading to some cultural and literary references.

The adult Common House Martin of the western nominate race is 13 centimetres (5.1 in) long, with a wing span of 26-29 centimetres (10.2-11.4 in) and a weight averaging 18.3 grammes (0.65 oz). It is steel-blue above with a white rump, and white underparts, including the underwings; even its short legs have white downy feathering. It has brown eyes and a small black bill, and its toes and exposed parts of the legs are pink. The sexes are similar, but the juvenile bird is sooty black, and some of its wing coverts and quills have white tips and edgings. D. u. lagopodum differs from the nominate race in that its white rump extends much further onto the tail, and the fork of its tail is intermediate in depth between that of D. u. urbicum and that of the Asian House Martin.

The white rump and underparts of the Common House Martin, very noticeable in flight, prevent confusion with other widespread Palaeoarctic swallows such as the Barn Swallow (Hirundo rustica), Sand Martin (Riparia riparia) or Red-rumped Swallow (Cecropis daurica). In Africa, confusion with Grey-rumped Swallow (Pseudhirundo griseopyga) is possible, but that species has a grey rump, off-white underparts and long, deeply forked tail. The Common House Martin flies with a wing beat averaging 5.3 beats per second, which is faster than the wing beat of 4.4 beats per second for the Barn Swallow, but the flight speed of 11 m/s (36 ft/s) is typical for hirundines.

The Common House Martin is a noisy species, especially at its breeding colonies. The male's song, given throughout the year, is a soft twitter of melodious chirps. The contact call, also given on the wintering grounds, is a hard chirrrp, and the alarm is a shrill tseep.

The subspecies D. u. urbicum breeds across temperate Eurasia east to central Mongolia and the Yenisei River, and in Morocco, Tunisia and northern Algeria], and migrates on a broad front to winter in sub-Saharan Africa. D. u. lagopodum breeds eastwards of the Yenisei to Kolyma and south to northern Mongolia and northern China; it winters in southern China and Southeast Asia.

The preferred habitat of the Common House Martin is open country with low vegetation, such as pasture, meadows and farmland, and preferably near water, although it is also found in mountains up to at least 2,200 metres (7,200 ft) altitude. It is much more urban than the Barn Swallow, and will nest even in city centres if the air is clean enough. It is more likely to be found near trees than other Eurasian swallows, since they provide insect food and also roosting sites. This species does not normally use the reed-bed roosts favoured by migrating Barn Swallows.

It uses similar open habitats on the wintering grounds, but the Common House Martin is less conspicuous than wintering Barn Swallows, tending to fly higher and be more nomadic. In the tropical parts of its wintering range, like East Africa and Thailand, it appears to be mainly found in the higher areas.

The Common House Martin is a migrant which moves on a broad-front (i.e. European birds are not funnelled through the short sea crossings used by large soaring birds, but cross the Mediterranean and Sahara). While migrating they feed in the air on insects, and they generally travel in daylight, although some birds may move at night. Migration brings its own hazards; in 1974, several hundred thousand birds of this species were found dead or dying in the Swiss Alps and surrounding areas, caught by heavy snowfall and low temperatures. Adult survival on autumn migration depends mainly on temperature, with precipitation another major factor, but for juveniles low temperatures during the breeding season are more critical. It is anticipated that since extreme weather is predicted to become more frequent with climate change, future survival rates will depend more on adverse weather conditions than at present.

The Common House Martin returns to the breeding grounds a few days after the first Barn Swallows; like that species, particularly when the weather is poor, it seldom goes straight to the nesting sites, but hunts for food over large fresh water bodies. There are records of migrant House Martins staying to breed in Namibia and South Africa instead of returning north. As would be expected for a long distance migrant, it has occurred as a vagrant eastwards to Alaska and west to Newfoundland, Bermuda and the Azores.