He worked his way up to cashier in 1879, the same year he became treasurer of the Freestone Savings Bank of Portland, which he later served as president.

He published over one hundred essays and articles in scientific journals, state publications, and local newspapers.

His book The Birds of Connecticut (Hartford, CT: State Geological and Natural History Survey, 1913) gained him recognition as the preeminent expert on the subject.

Sage bequeathed his personal papers and collection of 5,000 taxidermied birds to the Wadsworth Atheneum, where he had worked as curator of natural history.

[3] In 1946, the Wadsworth loaned the collection to Trinity College due to storage constraints and a shifting scope.