"Pesto, the viral baby penguin, is undergoing a natural process called fledging. At 10 months old, he's shedding his fluffy baby feathers and growing sleek adult ones, which will make him waterproof. This process typically takes 3-4 weeks and will allow him to swim with other king penguins soon after."

Source: https://ca.news.yahoo.com/pesto-growing-viral-baby-penguin-211200715.html