Dear Media, Please stop citing this guys numbers. Cheers, Greg
On April 17th, the NY Times published an article entitled: “At a Long Island Beach, Human Tempers Flare Over Claws and Feathers”. In this article, they state:
The fight comes amid growing concern nationwide about the impact of feral or stray cats on wildlife in general and birds in particular. Federal researchers have estimated that cats, including outdoor house cats and tens of millions of strays, kill 2.4 billion birds annually in the contiguous United States.
Where did that 2.4 billion number come from? The article sites another article. In that article they state:
In a report that scaled up local surveys and pilot studies to national dimensions, scientists from the Smithsonian Conservation Biology Institute and the Fish and Wildlife Service estimated that domestic cats in the United States — both the pet Fluffies that spend part of the day outdoors and the unnamed strays and ferals that never leave it — kill a median of 2.4 billion birds and 12.3 billion mammals a year, most of them native mammals like shrews, chipmunks and voles rather than introduced pests like the Norway rat.
The “report” that they cite can be found here. It is an article in the journal Nature Communications called “The impact of free-ranging domestic cats on wildlife of the United States”. You might remember this from articles such as this, this, this, this and, more recently, this.
I got involved in this when I was asked to review the paper for Alley Cat Allies. (Full disclosure, I was paid by them to review the Nature Communications paper and my full review can be found here.) In general, I found the entire paper unsuitable for publication in an academic journal as a result of the numerous major statistical flaws. I’m not alone in this belief. You can find others who question the validity of the studies here and here, for instance.
But if you’re looking for more massive bird death “estimates”, don’t worry. It appears that Loss didn’t stop at just estimating cat predation mortality. He has gone on to publish a whole series of papers (and landed a job at Oklahoma State) “estimating” bird mortality of different sorts:
- Refining estimates of bird collision and electrocution mortality at power lines in the United States: 12 – 64 million
- Estimation of Bird-Vehicle Collision Mortality on U.S. Roads: 89 – 340 million
- Estimates of bird collision mortality at wind facilities in the contiguous United States: 140,000 – 328,000
- Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability: 100 million – 1 billion
- The impact of free-ranging domestic cats on wildlife of the United States: 1.3 – 4 billion
Those numbers are huge! And I don’t trust a single one of them.