* Japanese name: Iwa tsubame
* Scientific name: Delichon dasypus
* Description: The translation of the Chinese name for this bird is smoky-bellied hair-leg swallow. It is also known as the Asian housemartin. It's a small bird, some 12-cm long, and is colored a dark steel-blue above and is white — not smoky — underneath. The throat is gray, and the underwings are gray-brown. Young birds are duller. Perhaps it's the wings that give the smoky name. Males give a "za-za-za" call. It has white feathers covering the legs and toes, hence the "hair-leg" part of the name.
* Where to find them: On cliffs and large buildings or bridges. Temples are also popular nesting sites. They build a cone-shaped nest of mud mixed with a special gluelike saliva, and line the nest with grass and feathers. It's considered auspicious if a swallow or housemartin builds a nest on your house — although given that this bird likes to nest on large buildings, you are already quite auspicious if one nests on your house.
* Food: Insects. Birds in this family — housemartins and swallows — like to skim low over the ground and water catching flies. They are highly maneuverable, with a fork-shaped tail and tapered wings, enabling them to twist and turn with speed and agility. Rock swallows will take pretty much any insect they can, including dragonflies, small beetles, mayflies and even moths and butterflies.
* Special features: Asian housemartins lay a clutch of three or four white eggs, usually twice a year. The male and the female both help build the nest, incubate the eggs and feed the chicks. Much of the life of the housemartin is spent in the air, and the bird is adapted to this lifestyle with its streamlined shape, large eyes to help with catching small prey at high speed, and small legs to reduce drag while flying. They are a migratory species, flying sometimes thousands of kilometers to spend the winter in Southeast Asia, especially Indonesia and Micronesia. It is a common bird, but there have been slight declines in numbers recently and that has meant it is classified as "amber" on the endangered list.
PHOTO COURTESY OF BIO-IMAGE NET