photo by @joelsartore | Though some folks think he's wearing a party hat, the distinctive peak atop a horned guan grows over time- chicks hatch with just a slight bump on the head. Slowly this growth takes form and reaches its full height when the bird turns two years old. A native to central America, the guan has suffered serious declines due to habitat loss and hunting. The bird shown here lives at the St. Louis Zoo (@stlzoo which hatched two chicks this year, an important milestone for this endangered species. Please follow me, @joelsartore, to see more species from the #PhotoArk. #bird #photooftheday #joelsartore by natgeo

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