Thomas Hardy's "The Darkling Thrush" -Elegy for the death of God and Nature?

In the last stanza of this poem, the poet is surprised at the happy behaviour of the bird : "So little cause for Carolings...". he does not understand the reason of this excitement: "His happy good-night air/Some blessed Hope..." Is "the thrush" possibly comparing itself with the mythological bird of the Phoenix?: "...to fling his soul/Upon the growing gloom". The tone of the poem is quite pessimistic. It seems as if there is no future for humankind; but for all this, don't you think that the role of the songbird is that of providing some kind of "Hope" to humanity? -As the speaker seems to lament the death of God and the death of Nature, could we say that the poem is written in the form of an "elegy" as it also laments the death of the nineteenth century? and what is worse, the newly arrived twentieth century does not seem to offer a better picture for humanity. :idea: