What physical characteristic differentiates the Gyrfalcon from other falcons?

The Gyrfalcon is distinguished from other falcons primarily by its thick and powerful body structure. Unlike many other falcon species that may have a more slender and streamlined build, the Gyrfalcon's robust body allows it to be an efficient hunter in a variety of environments, particularly in the harsh Arctic conditions where it is commonly found. This physical characteristic not only aids in its hunting prowess but also contributes to its ability to withstand colder climates.

In contrast, the other options do not accurately describe the Gyrfalcon when compared to its counterparts. While short and rounded wings, small heads, and dark-colored feathers may be traits seen in some bird species, they are not defining features that set the Gyrfalcon apart from other falcons. For instance, many falcon species exhibit a wide range of wing shapes, and feather coloration can vary significantly among different individuals, making these traits less distinctive in the context of identification.