Bay-breasted Warbler - Magee Marsh - Lucas County OH - 2013-05-05. Photo by Greg Miller. Nearly 1 out of every 5 sightings of this species in North America in May 2013 was recorded in NW Ohio (18.9%). eBird as of 11/29/2013.
Each year, birders from across the U.S. and around the World come to northwest Ohio to go birding. Spring in particular is a great time when visitors come by the tens of thousands and spend millions of dollars in the area. I do not have the exact numbers, but I am sure others do.
My final tally for this event was 187 species with only 30 species of warblers. Combined with my trip to Shawnee St Forest in southern Ohio the week before the warbler total would be 36 species. Ohio is certainly a great place to find warblers.