When is a duck not a duck?

Logan has recently taken quite an interest in drawing, in writing out letters, in spelling words, and in adding numbers. We have a preschool workbook that we sometime go through but the main impetus is his own (which I think is the best way!). He brought this first picture to me yesterday and told me that it was a bird that didn't use its wings because it didn't fly. So I said "oh, a flightless bird?" so he asked me how to spell that and labeled the picture accordingly. Then he drew a duck and asked how to spell duck. I was a little worried about how more formal homeschooling would fit into our daily routine but I'm starting to think it won't be as hard as I may have anticipated.