How do swallows build their nests?

The material of swallow's nest is relatively simple, that is, soil, swallow's saliva and grass roots are mixed together. They fly to rivers and ponds, peck at wet mud, integrate it into particles, and then bring it back, mix it with straw and residual feathers, and build nests under beams or eaves. When building a nest, swallows build mud in the nest and squeeze mud balls from the inside out, so although the nest is uneven outside, the nest is relatively flat inside.

The bird's nest is covered with light feathers, soft fur and fine debris, and it has become a very comfortable home. To build a new nest, it will take at least 10 days, and the male and female swallows will work together to build a 3-4 cm mud wall.

If the soil for nesting is not well obtained, or the beam is too smooth, a collision accident will occur, and all previous efforts will be in vain. At this time, the swallow will persevere, rebuild and build a new nest from scratch.

Extended data:

A slender body can reduce the resistance when flying. Swallow's wing shape has a high aspect ratio, which means that it can produce great lift and little resistance. However, this aerodynamic efficiency is at the cost of reducing maneuverability (for example, compared with short and wide wings), but this disadvantage is partially compensated by the forked tail, because such a tail can improve the maneuverability of birds.

The tail feathers of some species are very long, which can increase the lift. It acts like the flap of an airplane, ensuring the airflow to pass through the wings smoothly, and can delay the airflow when the swallow is ready to land, so that the swallow can stop flying without increasing the resistance.

Most species have short tarsal bones and weak legs, which are suitable for inhabiting rather than walking, but those who dig holes or nest on cliffs have strong claws.