Which of the following terms does not fit with the others?

The term "train" does not fit with the others as it refers to the process of teaching or conditioning a bird of prey, while the other terms relate to specific anatomical parts of a raptor.

Talon refers to the sharp claws of a bird of prey, which are crucial for hunting and grasping prey. Tarsus is the bone structure in a bird’s leg between the knee and the foot, playing a significant role in the bird's ability to perch and move. Hallux specifically refers to the backward-facing toe that allows raptors to grip their prey securely. Each of these terms describes important physical characteristics that are vital for the bird's functionality in the wild as a hunting predator. In contrast, "train" pertains to behavior and interaction rather than an anatomical feature.