Kentucky warblers were regularly found when the habitat was right. This species likes wet, mature hardwood forest. They are usually present with wood thrush.
The best way to identify this species is by call. This is somewhat difficult because the pitch is close to that of the more common Carolina wren and Cardinal. The difference is that the Kentucky Warbler calls five times and the pitch does not change as much as it does with the other two species.
We downloaded the call from this web site: http://sdakotabirds.com/species/kentucky_warbler_info.htm
Without a lot of luck, the highest level of confirmation is likely to be probable (on territory).