They won't bath in a water bowl that is too deep for them to stand up in, so try a bucket for a while. Anything too deep for them. And maybe put some tiny tubs out for the chi like coffee mugs.
Also we use strings of plastic bags to keep them away. At certain times of the year I have to put pantihose over my car mirrors to keep them off, they're very persistent.
The squarking on the chair deal is more likely baby birds trying to get their parents to cough up some food. Some strategically placed fishing line should stop that. Tape sticks to the corners of the chair and wrap some fishing line along it so they can't land on the back of the chair without hitting the fishing line. If the line is a little bit loose and waves around in the breeze - that's still effective.
I'd be very tempted - after providing the dogs with alternate water supplies - to take the bowl the birds like to bath in, fill it as per normal and then wrap it with fishing line or glad wrap. Also if you put a chair over the bowl or put it in a box or crate which is on its side, they may be less enthusiastic about using it as most of their escape routes would be cut off.
Use fishing line that is of a strength that is easy for all your dogs to break - just in case.