J. N "Ding" Darling the cartoonist and the naturalist are one and the same person. The famous Sanibel Island wildlife reserve is named for him, along with several others throughout the US. He did design the first duck stamp. He was legendary in the conseraation movement. According to several sources he got the nickname Ding because he often signed his cartoons D'ing as a contraction of his last name.
Given that the engraving is actually roughly carved into the stock and specifically says "D. N." and doesn't mention Ding at all, I think there is zero chance it is the naturalist/cartoonist.
Sometimes these things are hard to judge. I once saw a high grade AYA sidlock 12 gauge double at Jaquas. Very nice gun and the rib was engraved prominently "Johnny Carson Los Angeles California". I was taken aback but had never heard anything relating Carson and shooting. In addition, it for some reason seemed odd to me that he would have something like that engraved with a nickname. The store was non-commital about the inscription, so I didn't pursue it.
