I've added a jack near the switch so I can use a wall wart to power the feeder. while I continue to experiment. I found out that 5-5.5V is the optimal voltage range for my setup based on dispensing reliability and noise.

However, being the beginner I am, I found myself wondering why the voltage would go from 5 to 4.5 over the course of a day. Apparently these unregulated power supplies need a base load to keep them putting out the expected voltage over time, and the PIR and single 555 aren't drawing enough to meet that threshold.

So I'm going to dig up a diode and add a 1K or so dummy load that only affects DC-in, not the batttery. Ideally this would also keep a 5V USB charger or power bank up and running as well,

In the end the motor I'm using does not seem to require lots of current since it's a low voltage motor and the only load is an eccentric free-spinning one. 

UPDATE

Before I changed anything I did some more tests.

I tried a couple more wall warts and found that a USB charger is sufficient to run both the birdfeeder and the Pi Zero camera. The charger I use can put out 2.4 amps and has two USB ports so I can plug both the camera and the birdfeeder into it. I got a USB-to-5.5x2.1mm barrel jack cable as I did not feel like adding a USB port to the birdfeeder. Eventually, maybe adding a type-A USB jack would be nice since the USB-to-barrel jack cable is not something most people have laying around. The Pi Zero currrent draw takes care of keeping the thing on if it has a minumun current draw requirement.

So, no changes and using a single power source for everything. Plus USB chargers are pretty common. Will try it out for a few days. The previous power supply I used worked fine over time if I set it to 6 volts, but 5 works and is a little quieter.

ANOTHER UPDATE

Looks like 5V wall warts need some more investigation. After about a day the power dips to the point where the motors and sensors don't work properly. 6V works fine over time, so I went back to using one USB charger for the two Pi cams and a 6V wall wart for the feeder until I figure this out.