I have been feeding them for years in the same feeder and they have disappeared for a few days at a time. I figured some local crop is temporarily available and they've gone to nosh on it.
This time, though, it's been weeks. Actually, over 3 weeks now.
Our hummingbirds disappeared for about a month, but they are back in normal numbers now. No idea what happened.
any new windmills up in your area? the libs in the township legalized feral cats?