About Delichon urbicum lagopodum (Pallas, 1811)
This subspecies, Delichon urbicum lagopodum, is a subspecies of the western house martin. Adult western house martins measure 13 cm (5 inches) in length, have a wingspan of 26–29 cm (10–11 ½ inches), and average 18.3 g (21 ⁄32 ounces) in weight. Their upperparts are steel-blue, with a white rump, all-white underparts including underwings, and their short legs are covered in white downy feathering. They have brown eyes, a small black bill, and pink toes and exposed leg areas. The sexes look identical. Juvenile western house martins are sooty black, and some of their wing coverts and flight feathers have white tips and edging. D. u. lagopodum differs from the nominate subspecies in that its white rump extends much further onto the tail, and its tail fork depth is intermediate between that of the nominate D. u. urbicum and the Asian house martin. The western house martin's clearly visible white rump and white underparts in flight keep it distinct from other common Palaeoarctic swallows including the barn swallow (Hirundo rustica), sand martin (Riparia riparia), and red-rumped swallow (Cecropis daurica). In Africa, it could potentially be confused with the grey-rumped swallow (Pseudhirundo griseopyga), but that species has a grey rump, off-white underparts, and a long, deeply forked tail. The western house martin flies with an average wing beat rate of 5.3 beats per second, which is faster than the barn swallow's 4.4 beats per second. Its flight speed of 11 m/s (36 ft/s) is typical for members of the swallow family. The western house martin is a noisy species, particularly at its breeding colonies. The male's song, produced year-round, is a soft twitter of melodious chirps. Its contact call, also used on wintering grounds, is a hard chirrrp, and its alarm call is a shrill tseep. The western house martin breeds across temperate Eurosiberia east to central Mongolia and the Yenisei River, as well as in Morocco, Tunisia, and northern Algeria. It is a long-distance migrant that travels on a broad front to winter in sub-Saharan Africa. Its preferred breeding habitat is open country with low vegetation such as pasture, meadows, and farmland, usually near water. It also occurs in mountains up to at least 2,200 m (7,200 ft) elevation. It is far more adapted to urban environments than the barn swallow, and will nest even in city centres if air quality is sufficiently clean. It is more likely to be found near trees than other Eurasian swallows, because trees provide both insect food and roosting sites. This species does not normally use the reed-bed roosts preferred by migrating barn swallows. It occupies similar open habitats on its wintering grounds, but is less conspicuous than wintering barn swallows, and tends to fly higher and be more nomadic. In the tropical parts of its wintering range, such as East Africa, it is mainly found at higher elevations. As a broad-front migrant, European western house martins do not concentrate through the short sea crossings used by large soaring birds, instead crossing the Mediterranean and Sahara directly. While migrating, they feed on insects in flight, and usually travel during daylight hours. Migration carries significant hazards; in 1974, several hundred thousand western house martins were found dead or dying in the Swiss Alps and surrounding areas after being trapped by heavy snowfall and low temperatures. Adult survival during autumn migration depends mainly on temperature, with precipitation as another major factor, while for juveniles low temperatures during the breeding season have a larger impact on survival. Because climate change is predicted to make extreme weather more frequent, future survival rates for this species are expected to be more heavily influenced by adverse weather than they are currently. The western house martin returns to its breeding grounds a few days after the first barn swallows arrive. Like the barn swallow, especially when weather is poor, it rarely goes directly to nesting sites, instead hunting for food over large fresh water bodies. There are documented records of migrant western house martins staying to breed in Namibia and South Africa rather than returning north. As expected for a long-distance migrant, it has occurred as a vagrant east to Alaska and west to Newfoundland, Bermuda, and the Azores. There is also one documented record of a western house martin in Colombia.
