1. Because the bird's nest is built under the eaves of human beings, it will have many benefits. With the shelter of the building, the bird's nest can be protected from wind and rain, and the swallows can live more peacefully. Swallows like to nest under the eaves of human beings. Another important reason is that humans don't hate them. We even regard this situation as a blessing. This is because swallows are appropriate beneficial birds and are of great help to agriculture. Swallows spend a lot of time catching pests and feed on insects such as mosquitoes and flies. Swallows have about 4-6 chicks in each nest, which shows how many pests swallows have to catch to raise chicks, which obviously plays a huge role in agricultural and forestry production.

Swallows build nests not only to shelter from the wind and rain, but also to choose nesting sites. Careful observation reveals that the nesting place of swallows is usually out of human reach, and it is difficult for small animals such as cats or mice to climb up. This is because they also consider the potential dangers posed by humans and other small animals. Some naughty children may dig out the eggs, while small animals such as cats, mice or weasels may eat them. In fact, it is also a helpless choice for swallows to nest under the eaves of human beings, because swallows' nests are generally made of mud and can only be built in places that can shelter from the rain.

Some biologists say that the number of swallows is decreasing year by year. In recent years, we have really seen fewer and fewer swallows. The reason is actually related to us humans. It can be said that swallows have been passively influenced by human technological progress. With the progress of building technology, the walls of human houses are now smooth, and there are fewer and fewer places in the corridor under the eaves where swallows can nest in the mud, and the sealing of houses is getting better and better. Swallows can't fly into houses to build nests, and people's lives are more and more clean, so there are fewer and fewer places for swallows to build nests for the next generation in human houses, which is one of the main reasons why we rarely see swallows now.