On my FB, a friend queried that she thought the swan was the form that Zeus took, rather than attributing the swan to Apollon like I do. This was in response to a painting I had sudden inspiration to paint of Apollon in the form of a swan with worshippers standing before him each holding an egg pressed level against their chests. I can understand where this confusion can arise, since most of us are more familiar with the swans mythic associations with Zeus through the myth of Zeus and Leda and her four children born (two sets of twins, only one set fathered by Zeus, and the other by her husband). That said some may suggest that the swan belongs to Zeus and case closed.
However, this is far from the case. The swan has an intimate association with Apollon, particularly his singing swans. Most animals that are particularly sacred to a deity it can be said that it is because at some time the god was recognized in that form. To say that two gods cannot share the same would be a little difficult, since there are many examples of gods associated with the same animal and being offered the same animal in sacrafice. For example the goat can be associated with both Apollon and Hermes, Poseidon and Zeus both share the bull, lions I have seen some connection with Zeus, Apollon and Artemis, not mention Rhea and probably considerably MORE deities. Dolphins are sacred to both Poseidon and Apollon as well. I can go on and on and onnnn, but that would be rather pointless. I think these few examples illustrates my point.
Some people might in their personal worship may prefer to connect an animal to one god over another, however that cannot reduce the ties of the other god in question. That said, one may prefer to call the swan a form and animal of Zeus, while another may have stronger associations of it with Apollon 🙂 I recognize Zeus’s claim the swan but in my personal worship, the swan has more meaning for me connected with Apollon. For obvious reasons. Also while Zeus took the form once, there is a long mythic association of Apollon, swans, his worshippers and Hyperborea where the singing swans reside. So that is my perspective 🙂