Avian Dinosaurs

The Hoatzin is possibly one of the oddest birds on the planet. It is found in swamps and mangroves of the Amazon and Orinoco Delta. It feeds on fruits and leaves which is processes in a modified crop not unlike mammalian ruminants where the plant matter can ferment before being fully digested. While this is interesting, it is not what they are known for. The Hoatzin is famous not for being an odd looking bird with a funny way or processing food, but for its chicks which posses a unique feature.
These chicks have claws protruding from their wings. These claws recede as the bird matures to adulthood. The claws are on two digits in their "hand" which make up the wing. The chicks use them to clamber over branches, an adaptation especially useful in light of the fact that the adults will flee the nest at the first sign of a predator leaving the chicks to fend for themselves. The chicks will climb out of the nest and hide in the tree branches or drop into the water below as the nests are usually built over streams. Once the predator is gone the chicks then climb back into the nest to await the return of their parents. At a certain point the chick grows too heavy to rely on its claws for support, at this point the chick begins to learn to fly and the claws begin to diminish.
Feel how you will about the evolution of birds, but this seems like pretty good evidence of the link between birds and their dinosaur ancestry.

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