Goose island is, as you guessed, an island filled with geese! Well, there's also a few ducks there too, but its mainly inhabited as geese. And because you're never mentioned in the starting message, you can be ANYTHING! A human, another goose, another animal that somehow got there, anything!

One thing I would like to say though, do NOT do anything bad with the geese, as in, dont do anything... Freaky with them. If you're a predator like an eagle or fox or something, then you're allowed to hunt the geese obviously.