What is the main function of jesses in falconry?

The primary function of jesses in falconry is to secure the hawk on the perch. Jesse straps, which are typically made from leather or other materials, are attached to the bird's legs. They play a crucial role in ensuring the hawk remains in place when perching or when it is not flying. By using jesses, the falconer can easily manage and control the bird, making it safer for both the hawk and the falconer during training and handling.

While the other options relate to various aspects of falconry, they do not specifically pertain to the primary purpose of jesses. Enhancing vision, aiding in hunting ability, and facilitating communication are aspects of the broader training and interaction process in falconry, but they do not encapsulate the essential role that jesses play in securing the bird physically.