I would never have both of them out at the same time. One of your cockatiels could fly down onto the floor and your dog could mistake it for a toy or it's terrier instinct could take over and they could easily kill the bird.
One time I had my parrotlet out of it's cage and she flew towards Brooklyn and Brooklyn tried to bit her out of fear.
You also have to be careful about the placement of your bird cage(s). Another time I had my parrotlet in her travel cage and it was sitting on the floor. In an instant, Britney tried to bit my parrotlet through the cage. If I wouldn't have been there Britney could've killed the bird.
__________________ Kyle (me), Britney, Brooklyn, and Coral |