Cats Killing Birds BY THE BILLIONS... REALLY? - Cat Info Detective


Skye Blake-updated, white background

Greetings crazy cats! People love to talk about us cats.  Some say we’re killing too many birds and that makes us murderers and horrible alien creatures!

What??!!  Is that really true?

paw prints coming in from a distance

You don’t have to be a scientist to figure it out. Just use the ol’ feline common sense.

Here’s the scoop… I was snooping around a hot trail of scientific and animal conservation sites and papers that led me to interesting places and lots of questions.

tuxedo cat in tree

A Nature Communications article, “The impact of free-ranging domestic cats on wildlife of the United States”, was written by three experts, Scott R. Loss and Peter P. Marra, of the Migratory Bird Center, Smithsonian Conservation Biology Institute, and Tom Will of the U.S. Fish and Wildlife Service, Division of Migratory Birds.

Lets see what they have to say about cats killing birds…

Who Is Skye Blake?

Skye Blake-updated, white background

Skye Blake, Cat Info Detective, is a curious cat researcher (not a veterinarian) who sniffs out expert, reliable sources about cats, studies their information, then passes it on to you! 

Sometimes there’s not enough evidence for easy answers, so Skye gives you all sides, explains the situation as thoroughly and clearly as possible, and links you to experts on each page. 

All sources are at the bottom of each page so you can do more snooping.

What Do These Scientists Claim About Cats Preying on Birds?

Claim #1

cat watching birds (pigeons)

“We estimate that free-ranging domestic cats kill 1.4-3.7 billion birds and 6.9-20.7 billion mammals annually.  Un-owned cats 1defined here as “…farm/barn cats; strays that are fed by humans but not granted access to habitations, cats in subsidized colonies and cats that are completely feral.”, as opposed to owned pets, cause the majority of this mortality.” 2The impact of free-ranging domestic cats on wildlife of the United States“, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013

Wow… BILLIONS! That’s a lot of critters and I have to ask…

Black & white eagle flying - birds
  • How many birds exist in the world? 
  • How many die each year?
  • What kills them?
  • Disease, predators (cats, foxes, hawks), wind turbines3“The Cleanest Energy In the World”, podcast interview of Michael Shellenberger, Founder & President of Environmental Progress, by Greg Gutfeld,, running into buildings (skyscrapers, windows), falling out of nests, forest fires, tornadoes, hurricanes? 
flock of seagulls flying over ocean

How can we even know? 

In other words, nobody knows exactly how many birds die each year in the United States, nor what true effect the common domestic cat, feral or tame, has on this cycle of life.

Cats usually kill the weak, sick or injured birds (hate to admit it, but healthy birds are too fast for us… shh, don’t tell anybody).  

Doesn’t that help keep the bird population strong and healthy?

Is it even possible to measure these things exactly?  I wonder…

Claim #2

flock of birds - pigeons

“Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for US birds and mammals.  Scientifically sound conservation and policy intervention is needed to reduce this impact.”4The impact of free-ranging domestic cats on wildlife of the United States“, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013

If Cats Are the Greatest Killer of Birds, How Do We Know Humans Should Interfere?

gray & white kitten

Look what happened on Macquarie Island, “where the removal of cats caused an explosion in the number of rabbits, rats, and mice that harm native seabirds…”5Cat predation on wildlife – Wikipedia

These scientists admit…

Studies so far are all guessing!

hunting tabby cat

“Existing estimates of mortality from cat predation [killing] are speculative and not based on scientific data or, at best, are based on extrapolation of results from a single study.  

In addition, no large-scale mortality estimates exist for mammals, which form a substantial component of cat diets.”6The impact of free-ranging domestic cats on wildlife of the United States, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013 [emphasis added]

black cat licking his lips

More studies need to be done about cats killing birds, rodents and other critters, especially for large land masses…

The magnitude of mortality they cause in mainland areas [like the continental U.S.], remains speculative, with large-scale estimates based on non-systematic analyses and little consideration of scientific data“.7The impact of free-ranging domestic cats on wildlife of the United States, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013

This was written in 2013 and I found no newer accurate data.

sparrow on a branch

“…we also accounted for the proportion of owned cats allowed outdoors, the proportion of owned and un-owned cats that hunt, and imperfect detection of owned cats’ prey items.”8“The impact of free-ranging domestic cats on wildlife of the United States”, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013

How’s it possible to figure out these proportions?

Especially since they admit there’s no way to know how many un-owned cats exist.

How do they know the amount of “imperfect detection” of cats’ prey?

You can’t measure what you don’t know.

The “Un-Owned” Cat Population

cat on alert hunting

No precise estimate of the un-owned cat population exists for the United States because obtaining such an estimate is cost prohibitive, and feral un-owned cats are wary of humans and tend to be solitary outside of urban areas

In addition, human subsidized colonies of un-owned cats are maintained without widespread public knowledge.”9The impact of free-ranging domestic cats on wildlife of the United States, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013

My twitchy cat nose tells me they should have stopped at “more studies are needed” and admitted there’s not enough reliable data to draw any conclusions yet.  

Science Beakers with liquid

That’s just Science 101.

Haven’t they heard of the Scientific Method? 

An experiment can only have one variable to accurately measure and conclude anything.

There are just too may variables when trying to study cats, especially feral cats hunting and killing birds and other critters.

Don’t Draw Conclusions When the Data Doesn’t Support It

Tabby cat pouncing on a gopher

Even a cat like me knows you shouldn’t draw conclusions you want if the data doesn’t support it.

“Nearly all studies of un-owned cats report numbers or frequencies of occurrence of different taxa in stomachs and/or scats. 

For studies reporting numbers of prey items, we estimated annual predation rates by assuming one stomach or scat sample represented a cat’s average daily prey intake (for example, an average of one prey item per stomach or scat = 365 prey per cat per year).10The impact of free-ranging domestic cats on wildlife of the United States“, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013

flying birds

They’re assuming everything else is equal, all cats eat the same everywhere and the same amount every day. 

Not realistic! 

Estimates and averages aren’t facts.  A fact simply is – it exists, true, unshakeable and unchangeable.

It doesn’t need a consensus.

Another Study… Are Cats Killing Birds or Just Scaring them Away? Is It a Problem?

cat with mouse in mouth

Claim #3

“East Bay Regional Park District, CA: A two-year study was conducted in two parks with grassland habitat. One park had no cats, while but [sic] more than 25 cats were being fed daily in the other park.

There were almost twice as many birds seen in the park with no cats as in the park with cats. California Thrasher and California Quail, both ground-nesting birds, were seen during surveys in the no-cat area, whereas they were never seen in the cat area.

white cat lounging on patio

The researchers concluded ‘Cats at artificially high densities, sustained by supplemental feeding, reduce abundance of native rodent and bird populations.’ “11Domestic Cat Predation on Birds and other Wildlife“, American Bird Conservancy

There’s the assumption that the birds were killed by the cats.

But what if the cats only killed some and the others were smart enough to stay away? 

Did they return when the cat population was reduced?

tabby cat family outdoors-feral

Whether they ate them or not, the critters left the area where their enemies lived.

Is this a problem? That’s up for debate…

In some places it might be, in others it might not.

Too many of any species in a concentrated area tends to throw of the balance of nature.

Not enough data is available yet to know for sure.

My Own Conclusions… Cats, Birds & Studies

Orange & White Cat under bush- cats killing birds

All scientists should know better than to take studies of a local problem and draw conclusions for entire areas of the world based on them.

Unfortunately, too many people try to make facts fit their theories and agendas instead of drawing true conclusions when facts are revealed by scientific study.

Many of the studies done are about cats preying on endangered species of birds on islands. 

This is totally different than the continental United States.

bright red bird on branch - cats killing birds

For example, Hawaii is a chain of islands with an environment totally different from the rest of the United States.

It’s not honest or fair to apply data from studies there to the rest of the country.

The United States is different in every area of the country. 

Urban, suburban, country and farm, lowland, mountainous, plains, desert.

Cat looking intently at bird on branch

All these areas have different ecosystems and have to be studied locally to draw useful conclusions.

Cats may hunt differently from one area to another, depending on what birds, mice, and other critters are available.

It may be more difficult for cats to kill birds in a plains area than in a city… or vice versa.

cat watching a sparrow - killing birds

Some areas probably do have problems with too many cats affecting their environment.

A few examples are improperly managed trap/neuter/release colonies.

Food is readily available, not enough cats get spayed/neutered, and people dump their pets thinking somebody will take care of them.

island beach

The result is that these colonies grow larger instead of shrinking.

In these areas, it could be that some cats have to hunt birds and other prey due to competition for food from other cats.

Don’t Feel Guilty If You Have Cats

Tabby cat seaside climbing on wood chair

Pet cat owners shouldn’t feel guilty if their cat kills a bird now and then. 

Keeping them inside is a great idea (hey, we love a cushy bed), but some of us don’t do well trapped between four walls.

You know your situation best so you must decide on a setup that works best for all of you.  That’s my opinion anyway. 

(Humans sure could use some lessons from us cats on how to be content.)

Don’t Pay Attention to the Alarmists

Tufted titmouse - cats killing birds

Even the scientists, with all their guessing, say it’s not the pet cats that are the problem (if there is one).

An observation about humans… some seem to like using fear about the state of planet earth to get money from people and power/influence in government policy making.

Makes it awfully tempting for them to make science fit what they want.

Just the twitching of my cat detective nose smelling something amiss…

Other Questions to Ponder

cat watching mouse

How do they know those extinct birds aren’t supposed to be extinct?

What if it’s nature’s way and it makes things worse when people interfere and try to save them?

Just thinking out loud. I’d love to know the answers.

Curious about other crazy cat ideas? Check out “Hot Cat Topics“.

I’m off now to follow another trail… Happy Hunting!


Sources used on this website are either primary or secondary. 

Primary sources are always preferable and have the most reliable information because they’re original and directly referenced.

Scientific abstracts and data are good examples of primary sources.

Secondary sources are weaker because they usually consist of opinions or articles that give no sources of their own, although, sometimes they refer to primary sources.

When I use secondary sources most are those with some authority, such as veterinarian or cat behaviorist books and articles.

List of Sources

Domestic Cat Predation on Birds and other Wildlife, American Bird Conservancy

The Cleanest Energy in the World with Michael Shellenberger“, Podcast interview of Michael Shellenberger, Founder & President, Environmental Progress, by Greg Gutfeld

*Nature Communications, The impact of free-ranging domestic cats on wildlife of the United States, Scott R. Loss, Tom Will & Peter P. Marra, Nature Communications, pub. Jan. 29, 2013

Cat predation on wildlife, Wikipedia

Updated April 12, 2024

1 thought on “Cats Killing Birds BY THE BILLIONS… REALLY?”

  1. Joan Drinkwater

    Thank you for standing up for cats! Very interesting about how these studies are not exactly completely possible. They make cats seem like evil predators that are causing the enormous destruction of wildlife. I worry people will take action against cats to protect birds.

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