Uria lomvia, the Thick-billed Murre
A recent study of the wing-propelled diving bird Uria lomvia shows that it has the highest recorded flight cost among vertebrates. That is, this bird (which consumes 146 watts/kg while flying) is so well-adapted to using its wings for diving that its flying suffers. In other words, the Thick-billed Murre is half-way to becoming a penguin.
Scientific Gems 