Cats kill over one million birds in Australia every day, according to a study published on Wednesday, which shows that majority of the attacks are by feral cats -pets that are abandoned and left to fend for themselves.
The study found that feral cats kill 316 million birds and pet cats kill 61 million birds in Australia every year.
The estimates are based on results from nearly 100 studies across the country, each sampling cat density, and another set of nearly 100 studies across the country that assessed cat diet.
Professor John Woinarski, lead researcher of the study published in the journal Biological Conservation, said that while previous research has looked at the impact cats are having on Australia's mammals, this is the first nation-wide assessment of the impact of cats on Australia's birds.
"Everyone knows that cats kill birds, but this study shows that, at a national level, the amount of predation is staggering, and is likely to be driving the ongoing decline of many species," said Woinarski, from Charles Darwin University in Australia.
The study also found that the highest rates of cat predation on birds are on Australia's islands and in remote arid Australia, where the number of birds killed by cats each year can reach 330 birds per square kilometre.
In a second study the research team also looked at which bird species are at most risk from cat predation.
They found records of cats killing 338 native bird species - almost half of Australia's native bird species. This included 71 threatened bird species.
"We found that the birds most likely to be killed by cats are medium sized birds, birds that nest and feed on the ground, and birds that occur on islands or in woodlands, grasslands and shrublands," Woinarski said.
"For Australian birds, cats are a long-standing, broad-scale and deeply entrenched problem that needs to be tackled more effectively," he said.
"The number of birds killed by pet cats is also high, but I would like to commend pet owners who are containing their cats instead of letting them roam freely," said Sebastian Lang, Australia's Acting Threatened Species Commissioner.