How did Hardy treat the theme of death in "The Darkling Thrush."

Thomas Hardy's morose poem about the turn of the twentieth
century employs a bleak and wintry landscape as a metaphor for the death of the
nineteenth century and personification of the end of the century with the
"corpse":

The
land's sharp features seemed to be

The Century's corpse
[the dead body of the 19th century] outleant,

His crypt
[grave] the cloudy canopy,

The wind his
death-lament.

Clearly,
Hardy's despair and pessimism pervades his poem as in line two he describes the Frost as
"spectre-gray"; however, the artfulness of the verse offsets this gloom.  For the poet
becomes grateful to the aged thrush for its "full-hearted evensong./Of joy illimited." 
The frail and aged thrush has chosen

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...thus to fling his
soul

Upon the growing
gloom.

In the midst of the
death of the century, the intrepid little thrush comes, to sing bravely in protest and
in "Some blessed Hope" for the new century.