I've noticed the same thing, Deb, and I've had the same thoughts about seasons following drought years. From what I've read, many large butterfly populations abound in marshy areas; if those areas are dried up for a couple of successive seasons it can't help but lower numbers.
We still seem to have plenty of hummingbirds here, but there's so many good blooms for them this year that they're not coming to the deck feeders very often.