Silver Bird was not same location as Silver City.
Silver Bird was formerly Thunderbird. Later, Silver Bird became El Rancho H&C.

Yes, Silver City was owned by Circus Circus Enterprises.

The property now owned by an entrepreneur who proposed a new San Francisco-themed casino. However, I don't think it ever got to the city approval stage. Besides, there was a dispute/lawsuit with Ruffin (owner of Frontier) over use of San Francisco theme idea.