What distinctive marking is commonly found on a Peregrine Falcon?

The distinctive marking commonly found on a Peregrine Falcon is the malar stripe. This is a prominent dark line located on the face of the bird, running from the beak down to the throat area. The malar stripe is not only a key identifying feature of the Peregrine Falcon but also serves as a form of camouflage, helping to break up the outline of the bird’s head and reduce glare from sunlight while hunting.

While other options may seem plausible, they do not specifically represent a hallmark characteristic of the Peregrine Falcon. For instance, crests are more common among other bird species and are not a feature of this falcon. Shadow markings typically refer to patterns of coloration that might be found in other raptors but are not identified with the Peregrine. Brightly colored plumage, while appealing, does not define the Peregrine Falcon, which is known for its more muted but distinct color palette. Therefore, the malar stripe stands out as the correct answer due to its specific association with the species.