swallow

Swallow

This data is reviewed by the project of data compilation and application of Science Encyclopedia of science popularization in China.

Swallow is the general name of 74 bird species in Passeriformes. They are small in shape, narrow in wing tip, short beak in concave tail, weak in feet and not too many feathers. The coat is monochrome, or has metallic blue or green luster; most species are similar to each other. Swallows spend a lot of time catching pests in the air. They are one of the most flexible passerine birds. They mainly feed on mosquitoes, flies and other insects. They are well-known beneficial birds. Nest in tree holes or crevices, or drill holes on sand banks, or stick mud on the walls or protrusions of corridors, roofs, eaves in urban and rural areas. Each egg produced 3-7 eggs.

morphological character

1 genus of Passeriformes. It is a small bird with a length of 130-180 mm. It has a long body, a small and sharp mouth, a large chin, thin wings and forked tail, and a long wing tip. Most of its back feathers are blue and black, so it was called Xuanniao in ancient times. The tip of wing is long and easy to fly, the beak is short and weak, and the beak is wide. The feet are short and the claws are strong. There are 20 species in the world and 4 species in China, among which domestic swallow and golden waist swallow are more common. The front waist of the swallow is chestnut red, the back chest has irregular transverse bands, and the abdomen is milky white. The body shape of the golden waist swallow is similar to that of the domestic swallow, but it is slightly larger. This kind of swallow is chestnut yellow in the waist, very obvious and eye-catching, and has small black lines in the lower body, which is easy to distinguish from the domestic swallow. Their habits are similar to those of domestic swallows, but most of them live in mountainous villages.

Body feathers: the upper body is usually metallic blue black, green black, or brown; some kinds of waists have contrasting colors; the lower body is generally light colored (usually white, light yellow or fruit color). There are usually subtle differences between the sexes, but the males sometimes have more striking colors and longer tails than the females; the young usually have lighter feet and shorter tails than the adult.

Chirp: chirp is a simple and fast chirp or buzzing sound. Usually, the duration of chirp is longer and the syllable order is changeable.

Morphological function

A slender body reduces drag during flight. The wing shape of the swallow is of high aspect ratio, which means that it can produce a large lifting force with little resistance. But this aerodynamic efficiency comes at the cost of reduced maneuverability (e.g. compared with short and wide wings), which is partly offset by a forked tail, which improves the bird's maneuverability.

Some species have long tail feathers, which can increase the lifting force. Its function is like the flap of an aircraft, which can ensure the air flow smoothly through the wings. When the swallow is ready to land, it can delay the air flow, so that the swallow can fly and stop without increasing the resistance. Most species have short tarsals, small and weak legs, which are suitable for habitation rather than walking, but the species that burrow or nest on cliff rock surface have strong claws.

The above general description of the species of yanidae is not applicable to the river swallows of the genus. They look more similar to other Passeriformes, and their original species may be between the family swallow and other Passeriformes. The legs and feet of river swallows are relatively large, and the related muscle tissues are less degenerated in terms of area, muscle number and complexity. Compared with the wide and flat beaks of other swallows, their beaks are more robust and thick, and the bronchial rings in their vocal tubes are not as complete as those of other swallows. In addition, there are a series of plume branchlets on the edge of the lateral primary flight feathers, forming a hook like thickening layer, but its specific function is not clear.

distribution pattern

In winter, the food supply of swallows in temperate regions is greatly reduced, so many species migrate. However, unlike most other passerine migratory birds, swallows migrate in the daytime and fly at low altitude. In addition, they often forage on the way of migration, so their fat reserves are lower than other migratory birds of the same size. Species that breed in Africa often migrate with rainfall patterns, but the details are not known. Other species, such as the grey rumped swallow, seem to roam around and have no fixed migration routes.

In recent years, the distribution of many swallow species has expanded, because as they increasingly use buildings as nesting sites, these birds have been introduced to previously unknown areas. For example, the distribution range of red fronted swallows expanded southward to Kenya and Tanzania, while the cave cliff swallows entered the southern United States from Mexico. The change of environment will also lead to the change of distribution pattern. For example, the British population of the house swallow wintered in South Africa, where its range has now expanded westward due to increased rainfall.

food

Almost all species of the family swallow only eat invertebrates in the air, mainly insects. Plant food is only found in a few kinds of food, and the intake is very small. Only two colored tree swallows regularly ingest plant substances (mainly berries), which only occurs during the period of insect shortage. Yan is not the kind of opportunistic predator, who will not fly around aimlessly and eat plankton randomly in the air with his mouth open. Instead, they take the initiative to prey on specific prey. Sympatric species are often specialized to prey on invertebrates of different body types. As far as an individual of a certain species is concerned, it often chooses the largest prey it can get. The food of migratory bird species in wintering areas is usually different from that in breeding areas. For example, the proportion of ants in the food of domestic swallow will increase when it overwinters in Africa. In addition, the preference of a species for foraging varies between wintering and breeding sites. These changes are considered to be the result of competition between these migratory birds and the resident species in the wintering areas.

Reproductive biology

The common practice of group living and single mating was adopted in Yan. Male and female birds raise their nests together, while female birds are usually responsible for nesting and hatching. However, males are often keen to mate with other birds. In some species (such as Ziya swallow), there is a phenomenon of one male and more females, one male and two females mate.

Swallows usually breed from April to July. The swallow nests under the eaves of the farmhouse. The nest is made of mud and grass stem with saliva, covered with soft weeds, feathers, rags, and some Artemisia annua leaves. The nest is dish shaped. Two litters are bred every year, mostly from May to early June and from mid June to early July. Each nest lays 4-6 eggs. The second nest is less, 2-5. The eggs are milky white. Male and female hatch together. 14-15 days after hatching, the parent birds were fed together. The chicks fly for about 20 days and feed for another 5-6 days. The food is insects.

Related Poems

Double swallow by Du Fu

The journey food startles the two swallows and brings mud into this hall.

We should avoid dampness and heat.

The road to foster son is long.

This autumn, heaven and earth are here, and I am far away.

GUI Yan by Du Mu

The painting hall is noisy with songs and dances. People who go to the club don't look at it.

Long is Jiang Lou's companion. At dusk, I'm still waiting to lean on him.

Chinese PinYin : Yan Zi