Filmmakers exposed the eggs of some of the birds to the sounds of people and film cameras so that the birds would not be afraid of them later.
Jacques Perrin says in his commentary that his team tried to include emperor penguins (Aptenodytes forsteri) in the film, but weather conditions interfered, so they had to be satisfied with king penguins (Aptenodytes patagonicus) instead. Some years later, the makers of March of the Penguins (2005) succeeded in making an emperor penguin movie.
In the scene where the "wild horses" gallop through the flock of geese (about 22 minutes in), a cowboy herding them is briefly visible in the background.
Four years in the making.