What voltage?

I'm going to guess that this device can be run using the same type of transformer used to operate low voltage outdoor lighting. You can find these in the lighting section at HD or Lowes.

So you hard wire the birdbath light to the transformer - then does the transformer have a plug that goes into a normal outlet?

Yes, same as a cell phone charger, cordless tool charger, those are all transformers.

What output voltage is required? While others here are saying it is like a cell phone charger, those are not nearly 60W output. A 60W transformer will be larger than some will imagine.

Guessing again, 120v input to 12v output. Bigger than a cellphone charger, more like a laptop charger.

then does the transformer have a plug that goes into a normal outlet?

Yes, same as a cell phone charger, cordless tool charger, those are all transformers.

While others here are saying it is like a cell phone charger, those are not nearly 60W output. A 60W transformer will be larger than some will imagine.

My answer was strictly to this question only. Though thinking about it it could be hardwired. I was not addressing the output.

Just watch out that you actually get a transformer, and not an AC/DC power supply (an 'electronic' transformer.

While the electronic ones are fine for lights and other purely resistive loads, they will play havoc with a motor load and can cause overheating that burns up the motor.

A 60 W, 120 V input, 12 V output transformer is NOT going to be a small device by any means.
60 W at 12 volts is 5 amps, and the secondary wire (12 V output side) will be sized for this.