I was recently very surprised to be the target of several people in this group for having bird houses and domestic cats. Funny thing was I started a thread about a snake getting into one of my bird boxes and just mentioned that the snakes help control mouse populations along with my cats. According to those people I am enabling the extinction of whole groups of bird species. Some of the comments were:

“The snakes might not need to go after the birds nests if you kept your damn cats out of their habitat.”

“IMO it’s irresponsible to set up nest boxes on your property if you’re keeping multiple cats around.”

“That’s not a birdhouse, that’s a cat feeder.”

“Cats are an invasive species”. (Ok this one gets me. Not considering bobcats, “domestic” cats have been in North America at least since Vikings brought them. How many centuries must pass before a species is no longer considered “invasive”?)

The thread went on to host a sometimes heated discussion between those who believe cats are horrible biodiversity devastators and those who argue that farm cats are not a threat and useful to help control rodents. Even after I explained that I live on a forty acre farm in the very rural Missouri Ozarks, my cats spend nights indoors, I was told that my cats were contributing to the extinction of many bird species and death of billions of birds.

So I’ve done some research on the research. The tl;dr is:

The belief that domestic cats are responsible for the widespread destruction of bird species is simply not supported by the science. Emphasize the word “widespread.” They do kill significant numbers in urban, suburban and geographically confined areas but the vast majority of all kills (69%) are done by feral cats.

There are wide ranges within the estimates due to lack of quality data collection. This is not the researchers’ fault. It’s just not easy to count birds killed by cats with good specificity so they have to rely upon generalizations and assumptions. Much more research is needed.

Using the mean number of birds killed by cats based on these estimates, cats (mostly feral cats) might be responsible for roughly ten percent of annual bird deaths. However the most likely cause of reductions in bird population is loss of habitat due to man-made changes and climate change.

However, some people, including some of the researchers themselves, misrepresent the facts to extrapolate the data across wide ranges of environments, bird species, habitat and often blame cats for losses caused by many other factors (loss of bird habitat and other effects due to human activity, effects of other predatory species and the loss of larger predators, climate change etc.) An early researcher stated, “No animal that it can reach and master is safe from its ravenous clutches”. Another example was a recent New York Times article entitled, “Cats Are a Bird’s No. 1 Enemy”. (While that was true in the suburbs of Washington DC which were studied, if you went by the headline alone you would think cats were a bird’s “No. 1 enemy” everywhere.) This suggests bias which negates the arguments. The media have mischaracterized this data through widely speculative and biased headlines and articles. I suspect most people read the articles rather than the original sources.

Much of the data is derived from studies on islands, cities and other dense human (and therefore cat) populations. Even within the US there is little segregation of the data between urban, suburban and rural habitats.

I found only a few sources of data that reflect the reality within the US. I’ve included a list of the sources I studied below. Each of them have their own sources which are worth a read.

A few bits of data that stood out:

The studies that claim that cats kill the majority of birds in in stark contrast to the studies that blame this on habitat loss.

Most estimates of the number of individual birds killed by cats fail to compare those numbers to the number of birds in total in the studied population. In some cases they actually exceed the number of birds in total. You shouldn’t assume anything without understanding the impact of those losses. Also understand that many bird species, especially wetland birds, have thrived and increased due to the protection of their habitat from human caused destruction.

There are no credible sources of extinction of any bird species, due to cat predation, outside islands where prey and predator are geographically confined.

Most studies fail to segregate bird predation by cats in dense human populations versus rural areas. 97 percent of the US’s land mass is rural but only 19.3 percent of the population lives there. If you accept that cats live where humans do then you should accept that rural cats are not the problem.

It’s the bulldozers, farm tractors, needs of humans, and feral cats, not domestic cats.

My bird houses are where from one to six broods of bluebirds and chickadees successfully fledge each year. Having done this research I am confident that my four bird houses, and the population of local bird species, are safe from any significant damage by my cats, although I am reevaluating snake protocols…

Edit: Perhaps I should say what I think should be done. Since feral cats cause the greatest number of bird deaths caused by cats, followed by urban/suburban cats, we should support efforts targeted there. Legislation and incentives to get owners to spray and neuter can help. Trap and spay/neuter feral cats (although I haven’t read research on its effectiveness). Regulation where such would be accepted. Elimination of feral populations if humane (?) and accepted.

But ignore the headlines. Read and critically evaluate the original sources.

Sources (others included within these):

Loss, S., Will, T. & Marra, P. The impact of free-ranging domestic cats on wildlife of the United States. Nat Commun 4, 1396 (2013). https://doi.org/10.1038/ncomms2380

National Feline Research Council, Wildlife impacts of free-roaming cats: Estimates vs. evidence. Unknown https://www.felineresearch.org/post/issue-brief-wildlife-impacts-of-outdoor-cats

Rosenberg, K., Dokter, A., Blancher, P., Sauer, J., and six others. Decline of the North American avifauna. SCIENCE, Vol 366, Issue 6461, (2019) https://www.science.org/doi/10.1126/science.aaw1313

William S. Lynn, Francisco Santiago-Ávila, Joann Lindenmayer, John Hadidian, Arian Wallach, Barbara J. King. A moral panic over cats. Conservation Biology, Volume 33, Issue 4 (2019) https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/cobi.13346

America Counts staff, One in Five Americans Live in Rural Areas. US Census Bureau (2017). https://www.census.gov/library/stories/2017/08/rural-america.html