Cat colonies cause a host of greater problems, as well. They can be a threat to birds and other wildlife, disturb the peace via cat fights and agitation of indoor cats, and create an unhealthy environment with elimination in gardens and yards, rummaging through trash, and spreading disease.
Read this article about Creating a Safer World for Cats and Wildlife on the Humane Society Legislative Fund website.
American Bird Conservancy information about Keeping Cats and Wildlife Safe
WhyFiles info about what cats do outside.