They will challenge anything, even strong opponents, without fear. Their frequent fights help them become stronger.
(From Bulbapedia) Rufflet is a small avian Pokémon with a blue body. A large white plume of feathers covers its head and three tail feathers extend from its lower back. The feathery ruff extends down past its neck, covering the upper third of its body. Its face is blue with five pointed tips, resembling a mask and crown in contrast to the white feathers surrounding it. Extending from its forehead is a large feather, which is red on the lower half and white on the upper half. The split between the two colors on the feather resembles a zigzag pattern. Rufflet's beak is short and wide, with large eyes on either side. Each eye has a thick black iris with a small white pupil. Its yellow legs and feet are large in comparison to the body. Each foot has four digits: one backwards, and three forwards.
The thick, black talons on its feet are strong enough to break even the hardest of berries, and crack Shellder to consume their insides. Rufflet is extremely aggressive from birth and knowingly provokes opponents larger and more powerful than itself, including its own parent to gain acceptance. It sees this as a means of quickly getting stronger.
(From Bulbapedia) Rufflet, like Braviary, is based on the bald eagle, specifically a baby eaglet most likely, paralleling Rufflet's position as the start of its evolutionary line. Its color scheme is inspired by the red, white, and blue of the flag of the United States. The single plume on his head also derives from Native American culture.
Its ability to use its talons to crack open nuts and feed itself in the anime is similar to that of parrots, who are the only known bird species to do so.
(From Bulbapedia) Rufflet may be a combination of rough, ruff, ruffle, or Ruff and eaglet (a young eagle).