I've forgotten who made the comment about more natural food being available for hummingbirds, but I have to give that notion a big second. I don't think I've ever, in my twenty years of wandering Cherokee Park (Louisville), seen so much Jewelweed in the park, and I understand that to be a huge food source for migrating hummers. I know Jewelweed likes moisture, so I have attributed the huge jewelweed patches to the wet conditions we've had all summer. I had also attributed this, perhaps erroneously, to the fall and winter storms having opened up a bit more tree canopy in the park; it seems like all of the undergrowth is doing extremely well with a bit more sun. Both the spring and summer wildflowers have done very well there this year.