Which raptor is referred to as a "Jack"?

The term "Jack" in the context of falconry specifically refers to a male Kestrel or Merlin. In the world of falconry, nomenclature identifies males and females in certain raptor species, with "Jack" denoting male members of these species. Kestrels and Merlins are relatively small birds of prey, and the male birds tend to exhibit different plumage characteristics when compared to females, which includes generally being more colorful in the case of the Kestrel. This naming is part of the traditional terminologies used in falconry to distinguish the distinctions between genders, particularly when training or discussing specific individuals in the sport.

Other types of raptors listed in the options, such as the Gyrfalcon, Red-tailed Hawk, and Peregrine Falcon, have different terms used to refer to males or do not commonly use the geographical term "Jack" for identifying male birds. The naming conventions in falconry can vary across different species, reflecting the unique characteristics and complexities within the avian community.