In order to add life in the game's world, I plan to make a lot of non-gameplay stuff like the birds you can seen below. They do their bird's stuff, and when the player is detected, they escape. Speed and other variables may change, but the idea already works great. (click for full size)
Unrelated: my friend Mathias just began to work on concept arts and designs. Here is the very first official concept art for Cape Bleue. It's far from being finished so I shouldn't show it here... But I love it and couldn't wait.