What is "hackle"?

Hackle refers to the specialized feathers found on certain birds, particularly on the neck and upper back regions. These feathers are often long, slender, and pointed, and they play important roles in the bird's appearance, behavior, and communication. Hackles can be raised or lowered by the bird to express emotions or communicate with other individuals. When raised, they can create an intimidating or defensive display, making the bird appear larger and more threatening.