There is a saying in the countryside that "swallows don't worry about their homes". What is the truth?

Generally speaking, "swallows don't enter the mourning room", that is to say, swallows don't build nests or settle in unhappy and unharmonious families. Swallow, a very common bird, is quite spiritual and has a close relationship with human beings. Every spring, when flowers bloom, swallows will fly from the south, nest under the eaves and live with people. At this time, the roof of the farmhouse is actually the swallow's second home, where they thrive. Swallows are beneficial birds. They feed on mosquitoes and flies. Every summer, a swallow can eat hundreds of thousands of mosquitoes. Therefore, it will be considered a blessing to have swallows nesting at home. This proverb actually means that swallows are also particular when choosing their place of residence. They won't fly to those unhappy families to nest. Why is this? Because swallows like to live in a relatively quiet environment, after all, it is to breed offspring. And those "unhappy and unharmonious" families are prone to conflicts, making their chickens and dogs restless, and swallows naturally "don't enter the worry room". After observing this phenomenon, people naturally understand the truth, so they all expect swallows to nest in their own homes, which has become a symbol of family happiness.