Consists of birds.
... I admit that I'm stretching the definition of bird, and that one of them isn't a bird at all. But Bunnelby is incredibly important.
The deck takes advantage of the big variety of special energy cards that have released over the years, but special energy can't win on their own. That just results in a dependence on Porygon-Z, which while it isn't a bad deck, I didn't like how the reliance on special energies meant less recovery options. So instead, the deck utilizes Fire energies as well and uses Talonflame as an attacker. Swellow and Bunnelby can help even out the prize trade.