How can I figure out how much energy a hummingbird expends while hovering?

When a hummingbird, or drone, or helicopter is hovering, theoretically, it is doing no work. The potential energy change is zero and the kinetic energy is also zero. Yet we know it takes fuel to keep them in the air.
It there a rule of thumb to determine how much energy/fuel they are using to stay in the air?
Surely there must be, but I don’t see it.