This looks to be a pigeon messenger with his carrier for his pigeon on his back.
The participle is "digging." Most participles end in -ing. It modifies "man", describing what the man is doing.
He literary techniques and figures of speech included in Robert Browning’s poem “My Last Duchess” include the following (highlighted with italics):
Answer:
selves poys stories journey=journey stepsons children laws zons mice axes memkrandums
