First. This pattern is not too much complicated, but I think is not for beginners. Although most of the pattern is very simple, understand the pattern of Duck's feet could be a little hard if you don't have experience enough. Nevertheless, if you are an amigurumi beginner, I encourage you to try it. If you have any doubt you can contact me through this post's comments or emailing me.
Second. Notice that I used two different yarn sizes. The thickest one was used for body, head, wings and tail.The finest one was used for beak and feet. You must use the exact size indicated of yarn and hooks to ensure the work be proportional. If you make, for example, the beak using yarn and hook indicated for body, you'll obtain a beak too much big and the duck will look horrible!
I did't have time enough for write the pattern in three languages so, today, English pattern. Maybe next Sunday could publish the Spanish and Portuguese versions :)