Clarification: Nationality vs Ethnicity

I'd like to suggest some more subtext next to the Nationality field when editing, to go with the existing Please specify if different from country of birth text. I think I speak for everyone who edits regularly that that we have to do a lot of clean up when it comes to people putting ethnic backgrounds into this field, whether they're a citizen/national or not. Frankly, I think there's a large portion of people who don't understand the difference, so the extra clarification is warranted.