Whenever I come to Alsace, I always make sure that I go to the Petite Camargue once.
It is nice anytime of the year, but when the whether is warm take a pique-nique with you, there are tables available in a relaxing location for you to stop.
You can visit very quickly, if you want to, but if you like observing the wildlife, then I would say take your time.
Various birds can be observed (Herons, King fishers, ducks...) also 'ragondins', frogs ... However to see those, you need to stay put and take time