Ding Yan. It is small in shape, with pointed and narrow wings, a concave tail, a short beak, and weak and small feet. The plumage is solid or metallic blue or green; the sexes are similar in most species. Swallows spend a lot of time catching insects in the air and are one of the most agile passerines. They build nests in tree holes or gaps in trees, drill holes on the beach, or stick mud to walls or protrusions to make nests; they lay 3 to 7 eggs each time, and sometimes the eggs have spots. Distributed worldwide except in the coldest areas and extremely remote islands. Temperate species include migratory birds that migrate long distances. The barn swallow (Hirundo rustica) has a brown throat and forehead, a blue head, and a forked tail. It migrates throughout the world. The subspecies in the United States is called the barn swallow, which can spend the summer in Canada and overwinter in Argentina. There are 10 species in the genus Petrochelidon, which build flask-shaped mud nests. The red stone swallow (P. pyrrhonota) in California has a strong return instinct.
Swallows are a genus of the family Passerine. This genus of birds is small, with a body length of 13 to 18 centimeters. The wing tips are long and the tail is forked. The back feathers are mostly gray-blue-black, so it was called a black bird in ancient times. It has long wing tips and is good at flying. It has a short, weak beak with a wide slit, which is the beak shape of a typical insectivorous bird. The legs are short and have strong claws. There are more than 20 kinds of swallows in the world, including house swallows, white-rumped swifts, barn swallows, rock swallows, gray sand swallows, golden-rumped swallows and hairy-footed swallows. There are 4 species in China, among which barn swallows and golden-rumped swallows are more common. Different swallows have different living habits. For example, they are both swallows, the swallows of swifts are climbing birds, and the swallows of barn swallows and golden-rumped swallows are songbirds. Different species of swallows have different shapes. The building swallow is slightly larger, can fly high and fast, is black in color, has a metallic luster, and sings very loudly. It likes to nest under the high eaves of ancient pavilions and pavilions; the house swallow is smaller in size and has a metallic upper body. It is brilliant black, with a chestnut head and a white or light pink belly. It flies low and makes a quiet sound. It mostly builds its nests on the beams and corners of indoor houses of residents. It likes to be close to humans. Swallows usually breed from April to July. Barn swallows nest under the eaves of farmhouses. The nest is made of mud and grass stems glued together with saliva, and is covered with soft weeds, feathers, rags, etc., as well as some Artemisia annua leaves. The nest is dish-shaped. Two litters are produced each year, mostly from May to early June and from mid-June to early July. Each clutch lays 4 to 6 eggs. The second clutch is smaller, with 2 to 5 eggs. Eggs are milky white. Male and female eggs hatch together. The young birds emerge from their shells at 14 to 15 days and are fed together with the parent birds. The chicks take flight in about 20 days, and after another 5 to 6 days of feeding, they can feed themselves. The food is all insects. The Golden-rumped Swallow is similar in shape to the Barn Swallow, but slightly larger. The waist of this kind of swallow is chestnut yellow, which is very eye-catching. There are small black stripes on the lower body, making it easy to distinguish it from the house swallow. Their habits are also similar to barn swallows, but they mostly live in mountainous villages. Swallows are typical migratory birds. After breeding, the young birds still follow the adult birds and gradually gather into large flocks, migrating south to overwinter before the arrival of the first cold wave.
Swallows are beneficial birds to humans. They mainly feed on insects such as mosquitoes and flies. They can eat 250,000 insects in a few months, so we cannot harm them. Swallows always make their annual long-distance journey in the autumn before winter comes - flying in groups from the north to the far south, where they enjoy the warm sunshine and humid weather, leaving behind the harsh frost and coldness of winter. The cold winds leave the chickadees, grouse and ptarmigans that never fly south for the winter. On the surface, it seems that the cold winter in the north causes swallows to leave their hometown and go to the south to spend the winter. When spring comes, they return to their hometown to have children and live and work in peace and contentment. Is that true? Not really. It turns out that swallows feed on insects, and they have always been accustomed to catching flying insects in the air. They are not good at searching for insect food in the gaps between trees and ground, and they cannot eat berries, seeds and food like oak grouse and ptarmigan. Feeds on leaves instead in winter (coniferous species do not lose their leaves even in winter). However, in the winter in the north, there are no flying insects for swallows to prey on, and swallows cannot dig out the larvae, pupae and eggs of hidden insects like woodpeckers and woodcocks. The lack of food forces swallows to make a great north-south migration from autumn to spring every year in order to obtain a wider living space. Swallows have become the "nomads" in the bird family.