Which item is not necessary for a newly trapped bird?

A transmitter is not necessary for a newly trapped bird because its primary purpose is for tracking and monitoring the bird's location after it has been released or during training. Newly trapped birds typically need immediate attention to ensure they are comfortable and safely acclimatized to their new environment, which involves equipment directly related to managing their handling and physical safety.

On the other hand, a glove is essential to handle the bird safely and protect the falconer from potential injuries, while a swivel and a leash are required to provide control and prevent injury to the bird during initial handling or training. Thus, while a transmitter can be a useful tool in the long term for tracking an already trained or released bird, it is not a fundamental necessity for the immediate care and management of a newly trapped bird.