John R. Neill drew several strikingly similar illustrations of swans in flight. I mentioned in some earlier comments that the frontispiece color plate for Andersen's Fairy Tales featured wild swans, from the story of that name. This was one of three finished watercolors for the book, and this book is one of the few to use finished paintings by Neill.
This image makes me think of the drawing of Glinda flying in her swan chariot, from The Lost Princess of Oz, by L. Frank Baum. This was drawn about five years before the Wild Swans. The swirl of the flying swans in the air is very similar in both pieces.
Another lovely watercolor is the painting created for the endpapers of Peter and the Princess. Here again we see a swirling group of swans, this time landing in a lake. The original of this piece is being auctioned Sept. 17th by Bloomsbury Auction House, as part of the Fred Meyer collection.
Another Oz piece, this time with a single swan, is the drawing of the diamond swan, from Glinda of Oz - the diamond studded bird is the result of a spell on a character in the book. I always thought it might be interesting for Glinda to adopt this swan as the leader of her pack - unfortunately, the swan is so vain it would probably never agree to such work.