Swans

When Tolkien refers to swans, he would most likely have had in mind the so-called mute swan (Cygnus olor), which is by far the most common variety in the British Isles. We're also told of black swans to be found in the more southerly reaches of Anduin, but these are extremely unlikely to be modern black swans (Cygnus atratus) which are native to Australia. Rather, the black colour in this case is apparently intended to indicated the encroaching power of the Dark Lord.

Swan is a very ancient word and, seems to mean essentially 'singing bird', a curious derivation given that swans are among the least melodious of all birds. The name is perhaps related to the fanciful legend of the 'swan song', a beautiful song said to be made by a swan as it dies.