Sorry to keep pestering you! I can't find anything like this in my bird ID book. I imagine its another warbler. Seen in Rochester, MN, along a city park creek, about 6:45pm, May 12. He was well in the shade, and even at ISO800 I was underexposed. Didn't get a chance to change settings before he was gone.
Steve- You will kick yourself when you find out that this is one of the commonest warblers out there- the magnificent Magnolia Warbler. The pattern of yellow with black stripes and the head pattern are very characteristic. They are one of my favourite Canadian birds and seem so exotic with their colouration.
Na, no kicking required. I'm new to the warbler thing and its the first one I've seen! Now that I know what it is, I recognize it in my Smithsonian guide! Thanks again!