Wikipedia:Today's featured article/January 31, 2022

Delichon is a genus of birds in the swallow family containing four species named as house martins. These are chunky, bull-headed and short-tailed birds, blackish-blue above, with a white rump and white or grey underparts. They have feathering on their toes and tarsi. They breed in Europe, Asia and the mountains of North Africa. The common (example pictured), Siberian and Asian house martins all migrate south in winter, while the Nepal house martin is resident in the Himalayas. House martins nest in colonies on cliffs or buildings. Both parents build the lined mud nest, incubate the three or four white eggs of a typical clutch and feed the chicks. Aerial hunters of small insects, they may be caught by fast birds of prey and may carry fleas or other parasites. None of the species are considered threatened, although common house martin numbers have declined in parts of Europe due to poor weather, poisoning by pesticides and nest-site competition with house sparrows.