What metaphors are used in Self-Portrait by Adam Zagajewski?

The speaker's walks take him past the green perfection of trees. He longs to establish a sympathetic connection with the natural world in all of its multiplicity, as he tries to do with the music he listens to, but ultimately the trees express nothing. Black birds become "Spanish widows" waiting patiently for news of their drowned husbands, the striking metaphor suggesting the speaker's recognition of nature's more destructive aspect.