In Pokemon Black and White, there are a few game exclusive evolutionary lines that can’t otherwise be found in the opposite games. Two of those are the Rufflet and Vullaby lines. Rufflet and its evolution, Braviary, are only found in Pokemon White and Vullaby and its evolution, Mandibuzz, are only catchable in Pokemon Black. However, unlike Petilil and Cottonee, the Rufflet and Vullaby lines can’t be seen in the game opposite in which they’re found without trading.
Rufflet is known as the Eaglet Pokemon. It appears to be based off from an eagle chick, though the plumage surrounding its head resembles a Native American headdress. Its name seems to come from the words ‘ruffle’, ‘rough’ and ‘eaglet’. According to their pokedex entries, Rufflet will stand up to nearly any opponent – no matter their size or how strong they are. Their frequent fights are supposed to help them become stronger. Once Rufflet becomes strong enough, it evolves into Braviary starting at level 54. Braviary appears to be based off from a fully grown eagle, more specifically a bald eagle. Its pokedex entries state that they defend their friends without taking into account the risk of their own safety. Apparently the more scars a Braviary has, the more respect they get from others for their bravery. Its name most-likely comes from the words ‘bravery’ and ‘aviary’. Because the Black and White games are based off from New York City, it would make sense to include an evolutionary line that would bring the United States into the games. Their color scheme references the American flag. The evolutionary line also contains characteristics often used to describe Americans, as they normally are quick to enter a fight and protect their allies. Both are a male-only species.
Vullaby is known as the Diapered Pokemon. It seems to be based off from a newly-hatched vulture chick. Its ‘diaper’ seems to creepily resemble the upper half of a skull, its legs coming out of the suspected eye sockets of the skull. According to Game Freak, Vullaby was created by James Turner so that the Black and White games had an American feel. According to its pokedex entries, Vullaby are apparently unable to fly due to their small wings, though ironically it is still able to learn the HM Fly. They protect their bodies with bones they’ve found, though will shed those bones when preparing to evolve. They supposedly seek out weak Pokémon. Vullaby’s name comes from the words ‘vulture’ and ‘baby’. Like Rufflet, Vullaby evolves once it reaches level 54 into Mandibuzz. Unlike its pre-evolution, Mandibuzz was created by Ken Sugimori. Mandibuzz is based off from a vulture and is possibly cave-man (or in this case cave-woman) related. The ‘apron’ around its waist appears to be the lower-jaw of a skull. Mandibuzz’s name comes from the words ‘mandible’ (a reference to the lower-jaw like ‘apron’) and ‘buzzard’ – a term often used to refer to vultures. The Vullaby line seems to be the female-only counterpart of the Rufflet line.