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Invasive Mammals Are Pushing Native Birds To The Brink

By on December 13, 2016 in Conservation, In the News

Cat with Bird

Cats Among Biggest Threats to Global Biodiversity

(Washington, D.C., Dec. 13, 2016) Invasive mammalian predators are killing endangered species around the world at much higher rates than previously known and are “arguably the most damaging group of alien animal species for global biodiversity,” according to a recent study published in the Proceedings of the National Academy of Sciences (PNAS). The findings are the latest evidence that cats and other invasive species pose a major threat to birds and other wildlife worldwide.

Non-native mammalian predators have contributed to the extinction of 87 bird, 45 mammal, and 10 reptile species, and have helped put another 596 species at risk of extinction, according to the study by Dr. Tim S. Doherty and colleagues, most of whom are researchers affiliated with Australian universities. Chief among these predators are cats, which have negatively affected 430 species of threatened or now-extinct birds, mammals, or reptiles.

The researchers estimate that cats have contributed to the extinction of 63 species, including 40 bird species—approximately double the number of extinctions previously attributed to these non-native predators. Combined with introduced rodents, such as Norway rats, “cats are major agents of extinction, collectively being listed as causal factors in 44 percent of modern bird, mammal, and reptile species extinctions,” Doherty et al. write. Both cats and rodents negatively affect the most bird species.

“This comprehensive study confirms yet again just how dramatic an impact cats and other invasive predators are having on bird and other wildlife populations,” said Grant Sizemore, Director of Invasive Species Programs at American Bird Conservancy. “Its findings are striking evidence that the problem is even bigger than previously recognized.”

ABC remains dedicated to confronting the challenge of outdoor cats. “Cats are popular pets, and many of us at ABC have pet cats. Once introduced into the environment by people, however, these cats cause extensive negative impacts,” Sizemore said. “Native species are ill-equipped to defend against such effective predators.” Not only do these cats kill birds and other native species, they also spread diseases such as rabies and toxoplasmosis that put human and wildlife health directly at risk. “The only realistic long-term solution is to contain cats, which simultaneously protects cats, wildlife, and people,” said Sizemore.

Learn more about ABC’s commitment to combating the threat of invasive species and our campaign to keep cats indoors. A recent Q&A on ABC’s Bird Calls blog has more on why cats represent such a serious threat to our irreplaceable wildlife.

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American Bird Conservancy is the Western Hemisphere’s bird conservation specialist—the only organization with a single and steadfast commitment to achieving conservation results for native birds and their habitats throughout the Americas. With a focus on efficiency and working in partnership, we take on the toughest problems facing birds today, innovating and building on sound science to halt extinctions, protect habitats, eliminate threats, and build capacity for bird conservation.

Contact: Grant Sizemore, 202-888-7480

Feral Cats Drive Songbird Decline

By on February 2, 2016 in BirdWords
Feral Cat Feeding Station

Feral Cat Feeding Station

Cats can be great pets, low maintenance purring machines. Unfortunately, they are also active and effective predators.

There are many ways for birds to die. Among the human causes in the US, window collisions may kill a billion birds a year. Cars kill a fraction as many, some 200 million. Pesticides, power line and cell tower collisions, wind turbines, hunting, and oil spills may kill another 200 million.

But the big killer in the US is cats. It is estimated that outdoor cats kill 2.4 billion birds a year in our country. With the exception of habitat loss, this number dwarfs all other current human-caused bird mortality combined.

Many of the studies are small, but they reveal a grim pattern. Cats kill nearly 50% of suburban songbird fledglings. Pet cats average one wildlife kill per fifty-six hours outdoors. They eat or abandon most of their kills at the kill site, not on the owner’s doorstep – belying many owners’ hopes that their pet is too domesticated to follow its instincts. A University of Nebraska study pins thirty-three bird extinctions on cat predation worldwide.

Feral cats number between 30 to 80 million in the US, according to World Animal Foundation estimates. If their kill rate equals that of pet cats, simple arithmetic indicates kills of small animals – birds, lizards, voles, etc. – of nearly 8 billion per year.

Despite being an invasive species, domestic cats are often maintained in the wild. Well-meaning people develop feeding stations that create unnaturally dense colonies. These colonies turn city parks and neighborhoods into native species kill zones, contributing hugely to the declines of American songbirds.

Further, these feral cat concentrations create sinks for the spread of disease and suffering, Feline leukemia and panleukopenia are highly contagious, disabling diseases of outdoor cats. FIV – the cat version of the AIDS virus – spreads mostly through saliva in cat-fight bites.

People, too, are at risk from cat-spread disease. Rabies is found in three times as many cats as dogs, possibly because of their greater involvement with wild animals and the lack of vaccination.

The toxoplasmosis parasite, famous for warnings to pregnant women against cleaning cat litter, can infect any warm-blooded being but only reproduces in cats. Over 70% of cats are expected to carry the parasite at some point in their lives, and they release hundreds of millions of oocytes that can deliver the disease for years through gardens and parks where they defecate. In people, our immune system usually prevents symptoms. But the parasite attacks the brain and is associated with deafness, eye lesions, and a wide range of behavior disorders including Alzheimer’s, autism, obsessive-compulsive disorder, and schizophrenia.

Some solutions to these bird kill and public health problems are easy. Pet owners who keep their cats indoors will protect both wildlife and their cats.

Feral cat problems are tougher to tackle. Trap-Neuter-Release programs have been shown to be ineffective. Neutered cats still kill birds and spread disease, and neutering efforts do not keep pace with the influx of new cats. A single breeding pair can produce 400,000 offspring over seven years.

US governments spend over $50 million a year to reduce the problems posed by feral and stray animals. In Redding, city land is being used to support feral cat colonies.