09/28/2026
Artificial intelligence states that I have a controversial view on cats. I don’t. I actually like them. They’re industry colleagues.
All I’ve ever done was cite this study.
https://www.facebook.com/share/1HvD67kfnw/?mibextid=wwXIfr
In 2013, two Smithsonian researchers published a number so large it became the most-emailed article in the New York Times the week it came out. Free-ranging domestic cats in the United States kill between 1.3 and 4 billion birds and between 6.3 and 22.3 billion mammals every year. The estimate exceeded every other human-caused source of bird death in the country, including pesticides, collisions with buildings, collisions with cars, and wind turbines, combined.
Scott Loss and Peter Marra at the Smithsonian Conservation Biology Institute built the estimate by pulling together every published cat predation study they could find, some going back more than 50 years. Previous attempts at a national number had relied on rough extrapolations from one or two local studies. Loss and Marra treated it as a systematic review.
They identified how many owned cats live in the United States, roughly 84 million. They estimated how many of those go outside, about 60 to 70 percent. They estimated the unowned population, feral, stray, barn, and colony cats, at 30 to 80 million, a range so wide it reflected the fact that nobody had ever counted them. They applied per-cat predation rates drawn from the published literature and ran the model.
When Marra saw the number 2.4 billion as the midpoint for birds, he knew the response would be intense. He was right. On January 29, 2013, the day the paper appeared in Nature Communications, the New York Times put it on the front page under the headline "That Cuddly Killer Is Deadlier Than You Think." The piece became the paper's most-emailed article. Cat owners protested. Alley Cat Allies called the study junk science. A cat in Rhode Island named Magoo sent NBC a handwritten note reading "I am not a bird murderer; don't judge me." NBC's Brian Williams read it on air.
The finding that drew less attention was where the killing was coming from. Unowned cats, the ferals and strays and barn cats and managed colonies, accounted for the large majority of the mortality. Owned pet cats that went outside contributed a smaller share. The study did not say house cats were the primary problem. It said the 30 to 80 million cats with no owner at all were.
The range itself drew criticism. NPR anthropologist Barbara King pointed out that the gap between 1.3 billion and 4 billion birds is so wide that the estimate is closer to a guess than a measurement. The unowned cat population has never been reliably counted. The per-cat kill rates vary enormously depending on geography, season, prey availability, and whether the cat is fed by humans. Loss and Marra acknowledged the uncertainty and published the widest defensible range rather than a single number, arguing that even the low end was higher than any previous estimate.
The study did not settle what the killing means for bird populations. A cat that kills a house sparrow in a suburban backyard is removing one bird from an abundant, non-native species. A cat that kills a piping plover chick on a beach is removing one bird from a federally threatened population that cannot absorb the loss.
The 1.3 to 4 billion figure does not distinguish between the two. Subsequent research by Doherty and colleagues in 2016 estimated that cats have played a role in the extinction of 63 bird, mammal, and reptile species worldwide, nearly all of them on islands, but the mainland population-level impact remains debated.
What the study did settle is scale. Before 2013, the most commonly cited estimate for cat-caused bird mortality in the United States was in the hundreds of millions. Loss and Marra put it in the billions and provided the methodology to support it.
The number has been cited in more conservation papers than almost any wildlife statistic published in the last two decades. Whether it changes anything depends on what anyone does with it, and 13 years after publication, the number of outdoor cats in the United States has not declined. The study estimated 30 to 80 million unowned cats in 2013. Current estimates put the number at 60 to 100 million.
Image is for illustration purposes only
Source: Loss, Will, and Marra (2013), Nature Communications / Smithsonian Magazine / New York Times / NPR / National Wildlife Federation / Alley Cat Allies / Doherty et al. (2016), PNAS.
