Swallows are migratory birds that typically travel long distances to find warmer climates during the winter months. However, not all swallows migrate to the south with other birds for a few reasons:

1. Food Availability: Swallows primarily feed on flying insects, and during the winter months, their main food sources become scarce. Some swallows may choose to stay in their breeding grounds or migrate to areas where they can find enough food to survive.

2. Climate Adaptation: Swallows have the ability to adapt to different climates, and some populations have developed strategies to survive in colder regions. These swallows may choose to stay in their breeding grounds where they have established nests and adapted to the local conditions instead of migrating.

3. Habitat Availability: Swallows require suitable nesting sites, such as cliffs, barns, or other man-made structures. If these nesting sites are available in their breeding grounds during the winter, some swallows may choose to stay rather than migrating.

4. Energy Conservation: Migration requires a significant amount of energy, and some swallows may choose to conserve energy by staying in their breeding grounds where they can find alternative food sources or hibernate.

It's important to note that not all swallows exhibit the same behavior, and there are different species of swallows with varying migration patterns. Some swallows do migrate to the south like many other birds, while others may exhibit partial migration or choose to stay in their breeding grounds throughout the year.

Because happy prince told swallow to stay in his country with him,and help poor needy people by giving the precious things that has been decorated in happy prince's statue.