Slightly larger than the American Kestrel, the Merlin is much more aggressive in behavior and more powerful in flight than its smaller falcon cousin. Females are larger, as with most birds of prey. Plumage differs between the sexes: adult males are gray-blue above, females are dark brown. Under parts are a pale rufous-red, with dark brown streaks and spots. Legs are yellow; the wings are short, pointed, and angular; the tail is dark with many thin whitish bands; the head has a dark crown, and a much fainter mustache mark than seen on other falcons. In flight, the Merlin can be distinguished from the American Kestrel by its darker underparts and longer, broader wing shape; the barred tail of the Merlin distinguishes it in flight from its larger falcon relatives, the Prairie and Peregrine Falcons. Merlins tend to fly rapidly in a direct line from one spot to another with short, fast, continuous wing beats. These feisty birds will aggressively harass other raptors who come into their territory.