A bird that is "keen" could also be said to be . .

A bird described as "keen" generally indicates that it is highly motivated and enthusiastic about hunting or pursuing its prey. This eagerness can be associated with multiple states, such as being hungry, which drives the bird's instinct to hunt and catch food. Additionally, "sharp-set" refers to a bird that is alert and in optimal physical condition, ready to engage in hunting activities. Finally, the phrase "ready to kill" encapsulates the bird's focused intent on capturing and killing its prey during the hunt. Thus, all these interpretations collectively reflect a bird's readiness and enthusiasm, making "all of the above" the most comprehensive and accurate answer.