Last fall the migration appeared to began earlier. In 2010 I banded a Blackburnian and a Canada Warbler on 12 August; my first Black-and White Warbler was captured on 19 August (along with a second Blackburnian). The next day I banded three Chestnut-sided Warblers. I ringed over a dozen additional warblers as the month progressed.
Photos: Chestnut-sided Warbler (top); Ovenbird (second); Black-and-white Warbler (third); Mourning Warbler (bottom).