While many of us enjoy the company of our cats, studies show that these pets hunt many species of native birds and animals
It is becoming clear that some domestic cats are persistent hunters while others may be more opportunistic. The majority of cats will attack small ground dwelling birds such as the beautiful blue wren. Once common, the blue wren is now rare where cats dominate.

Small night animals are also hunted if cats are left to roam after dark. These include ringtail possums (endangered here in Western Australia), baby brushtail possums, bandicoots and small bats.

Cats are most active at night, especially at dusk and dawn. This corresponds with much of the activity of our wildlife. By keeping your cat confined to your property at all times, and indoors, or in a special enclosure or cattery between dusk and dawn you will protect your cat and our wildlife.

If you provide all their needs, desexed cats are happy to live in a suitably enclosed area.
Cats don't have an 'innate' need to roam – they need exercise and play, as well as lots of sleep all day

Desexing your cat (at the proper age) reduces the aggression in males, and prevents unwanted kittens
Placing a collar with a bell around the cat's neck will make it harder for your cat to hunt wildlife. Unfortunately this doesn't always work.
Never dump unwanted cats. Feral cats are responsible for the death of thousands of native animals every year.

If you have determined that the cat is stray or feral (not owned) you can contact your local council or shire for advice.
If the cat is a pet, but you are unaware of the owner, try writing a friendly note describing the cat, and asking the owners to contact you. Drop this in letterboxes of your nearest neighbours.
If you can't determine the owners contact your local council or shire for advice.
If you know the owners, try a friendly chat explaining the situation and ask them to restrain their cat from entering your property.
Spray visiting cats with a hose or water pistol. They will soon get the message that they are not wanted. This deterrent is effective and harmless.
Make sure bird baths and water bowls are well out of reach.
You must treat the cat humanely. You can be fined for mistreatment or causing injury.

Cat repellent and sprays and gels are available from many plant nurseries, pet stores and some hardware stores. You can also try making up your own repellent using a number of scents cats dislike. We suggest you try the following:
A mix of ground black pepper and chili
Scatter citrus peel (oranges and lemons) around your garden
Place pine cones around garden borders
Plant geraniums, marigolds and petunias, cats and wildlife apparently dislike these plants
Grow spiky plants near areas you want to keep cats away from (base of trees which attract birds)

Information courtesy of:
Native Animal Network Association