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

The term that does not fit with the others is "train." In the context of falconry and bird anatomy, the other terms—talon, tarsus, and hallux—refer specifically to anatomical features of birds of prey.

Talon is the sharp claw of a bird, particularly important for hunting and grasping prey. The tarsus refers to the part of the leg between the knee and the foot in birds and is often considered in the context of a bird's leg structure and morphology. Hallux is a specific toe that is typically opposable in raptors, allowing them to perch securely and capture prey effectively.

In contrast, "train" refers to the process of teaching a falcon how to hunt, behave, and interact with its handler. While training is a crucial aspect of falconry, it does not pertain to the physical anatomy of a bird like the other terms do. This distinction highlights why "train" is the outlier among the choices provided.