[Aiwendil]

Originally Posted by Galin

Or too much ado about nothing maybe?

I'm always up for some useless pedantry.

There is a possibility that occurs to me, and though I don't think I believe it I cannot at the moment think of any logical impossibilities in it. When Treebeard says:

Originally Posted by Treebeard

They always wished to talk to everything, the old Elves did. But then the Great Darkness came, and they passed away over the Sea, of fled into far valleys, and hid themselves, and made songs about days that would never come again.

. . . what if this 'Great Darkness' is not that of Melkor but that of Sauron? Various returns of Sauron throughout the Second and Third Ages could perhaps be described in such a way. In this case, the Elves 'passing away over the Sea' refers not to the original migration to Aman but to the slower exodus of smaller companies that continued through the end of the Third Age.

I admit this is a stretch, though, if for no other reason than that shortly thereafter Treebeard is clearly talking about the days before the end of the First Age.

Originally Posted by Galin

Or is 'Darkness' here meant to be distinguished from Great Darkness? And if so, maybe the split between the Ents and Entwives occurs later? But if so, what does Darkness refer to?

This seems the most viable solution to me. In particular, I would combine this with your suggestion:

Another possibility might be the time when Morgoth returns to Middle-earth after his captivity,

Suppose, then, that the 'Great Darkness', when, according to Treebeard, the Elves passed over the sea or hid themselves, refers to Melkor's domination of Middle-earth, before the Great March of the Elves into the West. Then the 'Darkness', when the Entwives crossed the Great River, was after Morgoth's return. This would make some sense, actually, for after Morgoth's return, his attention seems to have been directed primarily toward Beleriand, so it seems reasonable for the Entwives to go eastward toward lands where his power was less. And since the first rising of the Sun was not all that long after Morgoth's return, the Entwives can very well give their minds to 'meads in the sunshine'.

Of course, this has the drawback that it relies on a rather forced distinction between the 'Great Darkness' and the 'Darkness'. But I think that an allowance for this can be found in Treebeard's nature. To one as old as he, and one whose pace of life is so slow, the time that passed between the Battle of the Powers and Morgoth's return may not have seemed so very long, especially across the distance of the Second and Third Ages; perhaps he thought of the 'Great Darkness' as encompassing both, with the ages of Melkor's captivity a mere temporary respite.

But there's another problem. Treebeard makes it sound as though the Elves were going about their merry business, waking up trees and whatnot, when the Great Darkness came; and, as a reaction to it, many Elves crossed into the West. But this sequence of events isn't what happened at all. Melkor's domination of Middle-earth began before the awakening of the Elves. They were born into that Great Darkness. And it was not until after Melkor was overthrown that they passed over the sea - which they did not in reaction to Melkor's dominion (which was already ended) but in response to the summons of the Valar.

To be honest, I think the best answer is probably just that Treebeard was himself getting a bit muddled in his old age. With so many thousands of years of memories to deal with, that would be perfectly understandable. After a while I expect all the comings and goings of various dark lords would start to blur together.