Birds evolved not only wings, but many other adaptations that make it possible to fly. Feathers provide insulation, waterproofing, and a lightweight means to become airborne. Birds have honeycombed or hollow bones, reducing body weight. And instead of weighty jawbones and teeth, birds evolved a light and serviceable beak made of keratin. Most birds consume energy-packed foods rich in calories – like seeds, fruits, and meat, which add as little as possible to a bird’s payload. And what they eat is processed rapidly, so they aren’t weighed down by waste.

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