What does the encounter on the Great River tell us about Balrogs?

Late in The Fellowship of the Ring, the companions encounter a mysterious being that we only later discover to be a Winged Nazgûl. Though they aren't able to identify it, Legolas succeeds in shooting down its flying steed. These events, and the conversation that follows them, are often put forward as evidence in the 'Balrog wings' debate. Perhaps strangely, readers on both sides of the discussion see support here for their position. In this article, we'll look at the details of the event, with particular interest in its relevance to Balrogs and their possible possession of wings.

The events in question occurred on 23 February III 3019, above the rapids of Sarn Gebir on the Great River. After being attacked in their boats by Orcs on the eastern bank of the river, the Company made their escape to the western shore. At that point, they see something coming up out of the southern sky:

We also know that it gave off the air of terror associated with the Nazgûl:

From his position on the bank, Legolas fired an arrow from his bow, bringing down the great Winged Creature on the other side of the River. Later in the night, the Company discussed their experiences, and Gimli praises Legolas for his shot.

It is Gimli's response that ties this episode into the Balrog question:

At this point Frodo also makes a relevant comment:

After this, no more is said on the subject.

Perhaps the most common interpretation comes from Gimli's comment above. If the winged shape reminded him of the Balrog, then doesn't it follow that the Balrog must also have been winged?

On a purely literal interpretation, there may be some merit in this position. It does face one difficulty, though: the fact that all three characters are sure that the creature is not a Balrog (even Gimli is only 'reminded' of it). If all they know about the being Legolas shot down is that it is winged and fearsome, and they already know that the Balrog has these attributes, it should be natural for them to assume that the flying creature was a Balrog.

If Frodo, Gimli and Legolas spy a flying, winged creature, then, and all conclude that it isn't a Balrog, then that seems to form an argument against Balrog wings. However, this point isn't really much more conclusive than the alternative, because we can't dismiss the possibility that some other unmentioned factor came into play (such as the sense of fear it emanated, or a lack of fire and smoke) to show that the winged figure could not be a Balrog.

The story of the encounter on the River certainly connects Balrogs and Wings in an interesting way, and perhaps it even goes some way toward providing a definitive answer to the question of Balrog 'wingedness'. Without a little more information, though, it's hard to tell whether that answer is yes or no.