2013-02-21 / News

Study shows alarming trend that bird mortality is connected to felines

Report says cats kill more than a billion birds annually
BY KEN SHANE


While birds like the eastern screech owl aren’t susceptible to cat attacks, wind turbines do pose a danger to them. The one above was spotted in North Kingstown by Jamestown birder Paul Jones. 
PHOTO BY PAUL JONES While birds like the eastern screech owl aren’t susceptible to cat attacks, wind turbines do pose a danger to them. The one above was spotted in North Kingstown by Jamestown birder Paul Jones. PHOTO BY PAUL JONES Most people know that cats are no friends to birds. Feline owners often see their pets come in from outside with a bird in their mouth. What most people don’t realize, however, is the extent of the damage that cats are doing to bird populations.

Chris Powell is a Jamestown resident with a master’s degree in biology who worked for the state’s Division of Fish & Wildlife Service before retiring. He headed the local Conservation Commission for 27 years, and he is an avid birder.

According to Powell, recent studies have shown that a massive number of birds are being killed by domestic cats. He cited the fact that cats are healthier and live longer if they are inside cats, and suggested that keeping domestic cats indoors is the answer to the bird mortality problem – at least as far as cats are concerned.

“Even though cats may be domesticated, they are natural predators,” Powell said. “Their genetics say that they hunt things smaller than them. Sometimes they kill them, sometimes they don’t. It is part of their lifestyle to kill small mammals and birds. A domestic animal is a natural predator and if it’s outside it’s going to do what comes to it naturally, which is hunting and killing.”

Powell said that he had cats as a child and he and his wife had cats for many years. Their cats were allowed outside, but everything possible was done to keep them from killing birds.

“Most people never realized the magnitude of the problem until these studies were done,” Powell said.

The Journal of Ornithology recently did a study on the mortality of baby gray catbirds in the Washington suburbs. The study found that nearly 80 percent of the birds were killed by predators, with cats being responsible for nearly half of that number. Neighborhoods with large cat populations showed particularly high death rates.

According to a report (“The impact of free-ranging domestic cats on wildlife of the United States”) published by the American Bird Conservancy, free-ranging domestic cats kill 1.4 to 3.7 billion birds each year. They are also responsibility for 6.9 to 20.7 billion mammals annually. The report added that unowned cats, as opposed to pets, cause the majority of the mortality.

“Our findings suggest that freeranging cats cause substantially greater wildlife mortality than previously thought,” the report says, “and are likely the single greatest source of anthropogenic mortality for U.S. birds and mammals. Scientifically sound conservation and policy intervention is needed to reduce this impact.”

Much of the attention being paid to bird mortality in recent years has been focused on wind turbines, and in fact the turbines are responsible for more than 400,000 bird deaths each year, according to the U.S. Fish and Wildlife Service. That number is expected to increase as more turbines are erected, but it pales in comparison to the number of birds killed by cats.

“I think people would be horrified if they knew the numbers,” Powell said.

According to Powell, the damage is not only being done by domestic cats, but also by unowned cats that live in the wild. He voiced opposition to trap-neuterrelease programs that allow the cats back into the wild where they can continue to prey on birds and other mammals. The programs are widely supported by humane societies and other animal activist groups.

“They’ll tell you that there is nothing wrong with these programs,” Powell said. “Rather than capturing feral cats and euthanizing them, they trap them, they neuter them, and they release them. Sometimes they put feeding stations out for them. What they’re hoping is that in time the animals will get old and die, which they do. In the meantime, how much damage have these populations done to small mammals?”

Powell said that feral cats live in Jamestown, and that for a long time there was a trap-neuter-release program on the island. He added that while it’s natural for all cats to eat birds, domestic cats are not wild animals, yet they are having a major impact on other wild populations.

“We have a responsibility to protect the wildlife and enjoy our pets,” Powell said. “It’s the owner’s responsibility to ensure that their pet is not killing and eating wild animals.”

According to Powell, wildlife has evolved to do things a certain way. Birds migrate in certain unchangeable patters. When they run into something like a high-rise building, wind turbine or cat, they haven’t adapted in order to avoid those impacts.

Proper siting of wind turbines can help in reducing bird mortality, Powell says. Birds are efficient flyers, and raptors like owls and hawks tend to fly where the winds are good, which is also where turbines are located. The result is competing uses for that space. Turning the turbines off and on according to wind speed can also help to deal with the issue.

“We’re all just used to having cats and letting them out in the morning,” Powell said. “I don’t think that people realize the impact that they are having on wildlife, especially wildlife that has a lot of other pressures right now.”

Grant Sizemore is head of a program by the American Bird Conservancy to keep cats indoors. According to Sizemore, domestic cats that spend their time indoors make excellent pets. When allowed to roam freely outside of the home, however, cats are invasive predators. They are skilled at hunting and will do so without regard to hunger.

“Numerous studies have shown that even well-fed cats continue to hunt,” he said, “and that hunting behavior and hunger are controlled by different portions of a cat’s brain. Unlike native predators, whose populations are controlled by natural processes, cat populations are supplemented by their affiliation with people. This relationship enables cats to have an enormous impact on native wildlife.”

The American Bird Conservancy recognizes the risks to cats, wildlife and people as a result of allowing cats to roam outdoors. Consequently, the conservancy advocates for all cats to be kept indoors, on a leash, or otherwise constrained from roaming freely. The program is designed to educate cat owners and the public about the risks associated with free-roaming outdoor cats. It also serves as a resource for individuals and organizations interested in effective management options.

Sizemore said that restricting cats to the safety of homes, leashes or outdoor enclosures is an excellent way to protect wildlife. However, approximately 30 to 80 million cats in the contiguous United States do not have owners to care for them. Unowned cats are a major contributor to wildlife predation, do not have ready access to veterinary care, and require a different management strategy than owned cats.

“The negative impacts of the current cat overpopulation and large numbers of stray and feral cats necessitate removal of these homeless pets from the environment,” he said.

Sizemore said that the first two options for these wild cats should be adoption or placement in an enclosed sanctuary. If those two aren’t available, according to Sizemore, then euthanasia becomes the solution.

“Trap-neuter-release is an ineffective management option that sacrifices wildlife for the irresponsible behavior of pet owners,” he said.

Sizemore said that trap-neuterrelease colonies do not reduce cat populations. Additionally, he says the programs increase the likelihood for disease transmission and only encourages pet abandonment.

“Domestic cats were introduced to the United States with the arrival of people from Europe,” said Sizemore. “Cats are not native and are not a natural part of functioning ecosystems in this country. Cat predation is another human-caused source of mortality that adds to the already enormous pressures placed on native bird populations. In order to conserve bird species and other wildlife for future generations, it is time for people to stand together to demand a responsible policy to keep cats indoors.”

Return to top