It probably wasn't what the author intended, but I think this story is a great metaphor for homeschooling. Gooseberry is a little goose who is having fun practicing flying all day, but he meets different friends getting ready for winter (like a squirrel gathering nuts) who warn him that he won't be prepared when winter comes. At the end of the day, Gooseberry goes home to his parents and says that they have to get ready for winter! Gooseberry's parents laugh and tell him that since geese fly south for the winter, he's been getting ready all day--even though it felt like he was just playing.
Other people often think that homeschooling won't prepare kids for the "real world," and that they're not learning the things they will "need." But a different education simply prepares a kid for a different kind of life. We want our kids to have a zest and excitement for learning, like Gooseberry has for flying, not frantically trying to gather knowledge in preparation for a test, like a squirrel gathering nuts. After one winter, those nuts will be gone--just like kids (and adults!) often forget knowledge immediately after the test. But Gooseberry will be using his flying skills all his life--and I hope for my kids to be able to "fly" to new places, like Gooseberry, instead of hiding away in the difficult times of their lives.
Of course, this was just what I got out of the book. It could be interpreted many different ways! And it's not at all moralistic; kids will enjoy it just for the story.