Song thrushes and mistle thrushes often sing from the same treetops in early spring, and the app’s match percentage can be close between them (sample note).
Listen for repetition. A song thrush repeats each phrase two to four times before it moves on; a mistle thrush sings shorter, wilder phrases without repeating them, often in wind and rain.
If the match shows both, tap the reference song for each and compare. Then save the one you hear repeating.