A new American study has found domestic cats kill billions of birds and small mammals across the United States each year and last week in New Zealand a well-known economist called for the eradication of all cats due to their toll on native birds, reptiles and mammals.

In Ottawa, cats are also being blamed for maiming and killing large numbers of birds spurring some bird enthusiasts to call on cat owners to keep their pets indoors.

Patty Summers, a staff member at the Wild Bird Care Centre, said she agrees.

Earlier this month, after being clawed and bitten by a cat, a mourning dove was brought in for treatment, one of 300 wild birds treated there each year.

Summers said most birds are brought in by cat owners.

Strays, feral cats the worst offenders

The study by US scientists found the worst offenders are strays and feral cats — cats that live in the wild. Many of these cats live in colonies and they are often supported by cat lovers.

There are several colonies of feral cats in Ottawa but even some cat lovers are getting tired of them.

"My concern is they roam all over the yards and then they do their business on the yards," said Rosina Gagnon.

But Frieda, who lives nearby and declined to provide her last name, feeds and shelters the wild cats. She argued her feral friends or any outdoor cat are performing an important service.

"If you happen to have mice or rats, the cats will go after the mice for food," she said.

The Ottawa Humane Society regularly captures feral cats — neuters or spays them — and returns them to the wild. But the society also encourages cat owners to keep their pets indoors.

Preserving local songbirds is not the only reason why Eileen Barak, director of outreach at the humane society, recommended cats stay inside.

"Outdoor cats have a shorter livespan," said Barak. "They can run into complications outdoors which can be a danger to their health."