Why the poem by Thomas Hardy "By the Century's Deathbed" was changed to "The Darkling Thrush"?

Although the poem was written in 1900, literally at the very end of the 19th century and therefore at the century's deathbed, Hardy probably thought better of such a depressing and relatively unpoetic title.

For though the poem starts out with a bleak and depressing tone:

I leant upon a coppice gate

When Frost was spectre-grey,

And Winter's dregs made desolate

The weakening eye of day.

The tangled bine-stems scored the sky

Like strings of broken lyres,

And all mankind that haunted nigh

Had sought their household fires.

and then continues on equally dark and gloomy, by the third stanza the sound of the thrush is heard that rescues the day (and maybe the century).

Hardy probably thought better of the name of his poem, because, although it doesn't start that way, it ends with hope for better things, at least better than a whole century on its deathbed.

Coincidentally, Robert Frost expressed a very similar idea in his poem "Dust of Snow":

The way a crow

Shook down on me

The dust of snow

From a hemlock tree

Has given my heart

A change of mood

And saved some part

Of a day I had rued.

In both poems, a bird redeems all. Wow.