I've had a pond for 11 years that has not acquired fish. It existed before that, too, but I'm not sure for how long (I think several decades).

It has lots of amphibians and snakes. Rarely any birds.

Maybe the snakes have been eating the fish eggs / baby fish?

The bullfrogs are the big carnivores, and sure, maybe.

Snakes are active but I doubt they eat nearly as much as the bullfrogs.

	▲	giancarlostoro an hour ago \| parent [-]
		Apparently if you introduce a large fish species to your pond, the bullfrogs will not eat them, not sure how you would secure the eggs though. Maybe some sort of area that could shelter from them, but once they come out of shelter when they hatch, its kind of the same problem. Could also introduce fish that will eat the frogs to keep them under control. Or just leave it all as-is.