Hey Brant...just saw this subject line.
As Joel, I suspected water also.
As you mentioned the "bubbler" I use (in the backyard) is perfect for the HBs; i.e. makes gurgling and splashing noises that HBs love and the water doesn't have any depth, just a gentle waterfall type movement.
In the side yard, where all the seed and suet feeders are, I have a heated birdbath. It's plugged in for winter and unplugged for the warmer months. It's very popular w/all the birds and woodland creatures year round. I highly recommend it for those of us in colder climes.
I'll be interested in hearing about your experience w/the solar powered bird bath accessory.
Everybody stay safe and healthy
Bill