It has been my experience that the warblers come to Ontario when the leaves come on the spring trees. Usually that is the 1st or 2nd week of May. Here we are ending the first week of June and I can't find any warblers.
Maybe they will nest where they are and not come up here this year, I hope not.
We went to a favourite site today, Lake of the Mountain in Prince Edward County, (in Lake Ontario)where we have seen warblers in the past.
When no warblers were in sight or earshot, I crossed to the lake and did get a nice substitute - a flock of cedar waxwings were swooping around getting what insects were available. That is my favourite bird, although I don't see it very often. We once had a flock in our yard, but most times it is near a body of water.
The swallows were back at least, but no sign of a warbler yet.