Can English Cocker spaniels be trusted off-leash and are they good with parakeets and finches?

After being properly trained they can be trusted offleash in a safe area, but remember that they are hunting dogs, and they chase and pounce on birds. You will have to train the dog to leave the birds in your home alone; I'm not sure it would be kind to keep a bird dog in a house with birds he cannot touch.