Dad's neighbour has a black walnut tree that over hangs my parents' yard. Every year, they are inundated with walnuts.
When I'm there, I help him pick them up off the lawn. He stores them in his shed until winter, when he puts them out for the squirrels (mostly for the amusement of Ladydog). He got so many this year, that I thought I might bring some home for my squirrels