Here is my opinion on this subject:
I believe cat owners should have to follow the same laws as dog owners. You want your cat outside tie it up. Cats are the largest predator of song birds in the US.
http://www.wausaudailyherald.com/wdhopinion/283110016222044.shtml
A University of Wisconsin study of free-ranging cats - that is, cats that live in houses, barns or other structures but are allowed to roam at will - found that the animals do incredible damage.
One free-range cat alone can kill 200 birds and small animals in a year, and the study estimated that as many as 2 million such cats live in Wisconsin.
"Many cat owners believe that because they keep their cat well fed it doesn't need to kill," DNR wildlife biologist Nancy Christel said in a 2004 DNR newsletter. But studies have shown that well-fed cats kill as often as hungry ones. Domestic cats kill for play, not out of necessity, she said.
And that's to say nothing of truly feral cats - those that no longer have contact with people and kill to survive. If you've ever run into one, you know they are no more like Fluffy at home than are bobcats or lynx.
http://news.nationalgeographic.com/news....ts.html
Ron Jurek, a wildlife biologist for the California Department of Fish and Game, has kept a close eye on the impact feral and free-roaming domestic cats have on native species, like the California least tern, a federal endangered bird that nests along the coast.
"Cats do kill wildlife to a significant degree, which is not a popular notion with a lot of people," he said.
In urban areas, he said, there are hundreds of cats per square mile (1.6 square kilometers)—more cats than nature can support.
Exact numbers are unknown, but some experts estimate that each year domestic and feral cats kill hundreds of millions of birds, and more than a billion small mammals, such as rabbits, squirrels, and chipmunks.
Feline predators are believed to prey on common species, such as cardinals, blue jays, and house wrens, as well as rare and endangered species, such as piping plovers and Florida scrub jays.
For more than ten years, Jurek says, feral and domestic cats have been a persistent problem in California, killing one or two colonies of least terns each year. The small white birds are part of an intense monitoring program with a tremendous number of volunteers who watch the colonies throughout the six-month nesting season.
"If a cat finds the colony, it can destroy the colony in a few days, if not overnight," Jurek said.