In Jules Renard's poem "Swallows", swallows are described as being agile and intelligent.

In addition, swallows in reality have the following characteristics:

1. The swallow’s body is streamlined, and its two wings are narrow and long. They can vibrate 20 times per second. The tail is almost one-third of the entire body length, which is particularly important for flight. The swallow's body is particularly dexterous, with an average weight of only 20 grams, making it the most lightweight pilot.

2. Swallows are always flying, as if they never feel tired, but everyone knows that this is caused by their own weakness. Swallows have two very small feet. The thin feet cannot support the swallow's body, making them unable to maintain balance flexibly when standing on the ground.

3. Swallows have very strong reproductive capabilities and can lay eggs three times a year, with 3-7 eggs each time. This strong reproductive capability is in line with the need for the continuation of the swallow population, because swallows are a kind of Long-distance migratory birds.

4. Swallows are hard-working birds. They are busy building nests, "marrying wives and having children", and raising children all day long.

5. Swallows are good at flying, and their flying speed can reach 120 kilometers per hour. They are considered to be one of the best flying members in the bird family.

To sum up, the swallows written by Jules Lenard combine the various characteristics of swallows in reality and vividly reflect the agility and intelligence of swallows.