There is either one or no errors in the following statement.
Every spring in rural Vermont the sound of sap dripping into galvanized metal buckets signal the beginning of the traditional season for gathering maple syrup.
There are two things I don't see right, one of which is obviously the culprit.
- Directly after "rural Vermont" [Shouldn't there be a comma after it]
- "signal" [The subject is "sound" (singular), so the verb should end in an s.
I'm more on the side of the second one rather than the first. Or there could be no error at all.