Pigeons were introduced to Australia by the early European settlers and since then, they have rapidly increased in number due to the easy-to-access nesting places and abundant supply of food and water. They mostly feed on seeds and grain, fruits, small insects, vegetable matter, and some garbage and grit. Pigeons tend to feed, nest and roost in the same places (why homing pigeons where used as message carriers during the old days), breed all year round, and do not migrate far from their birthplace; this makes their removal a bit difficult. In city areas they feed, fly and roost by the hundreds. Their droppings can deface buildings and statues, and can be a nuisance to some motor vehicle owners. They are also carriers of many diseases, some of which are virulent, including pigeon ornithosis, encephalitis, and aspergilloses. The most effective way to deter pigeons from invading houses and public areas is to stop feeding them and to remove any potential food sources in open areas such as pet food. Pigeon-proofing buildings can also help in preventing these birds from gaining access to potential roosting and nesting areas.