Hunting and Scavenging
While the human environment carries risks for a cat, it has to be admitted that cats can also make trouble for other animals or humans.
Cats are natural born killers: we might find this distasteful, but it is a relevant fact. Hungry cats will kill only to eat; well-fed cats kill more frequently, and simply for the excitement of the hunt.
Cats will prey on whatever is available. Indoor cats are restricted to flies, moths, maybe mice, and occasionally our ankles. Outdoor cats have real birds, small mammals, and frogs.
This is potentially catastrophic to resident wildlife: there is at least one instance, off the coast of New Zealand, where one single cat drove a species of bird, the Stephen's Island wren, to extinction.
There may be no threat to the bird population where you live, but it is still your responsibility to ensure that your cat causes as little harm as possible.
Wherever you live, if your cat shows an inclination or ability to stalk and kill birds, do what you can to stop it. For example, do not set up a bird- feeding table in your garden, and attach a bell, or two, or three, to your cat's collar.
There are devices available for use in your garden to deter birds from landing. Investigate whether any of these is suitable in your circumstances.