A group of people sift through the leaves underneath a tree in a Chicago public park. There are probably lots of things you can eat in the city's parks. In New York, the city actually had tours that show you all the edible things in Central Park. I don't know if there's a similar tour available in Chicago.
I also don't know what kind of nuts or fruits or berries they were gathering. They didn't speak any English. Here's a picture of the tree's fruit. If you know what it is, post it in the comments section of this page, or in our Chicago discussion forum.