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Comment by poulsbohemian | Hacker News Reader

>I love cats but some of them absolutely do decimate local bird populations in the local neighborhood when they are left out unsupervised.

Not disagreeing per se, but every time this comes up on HN or in other public discourse, I ask for sources. Specifically, there is a statement that I see used regularly (including from the Audubon Society) that makes claims on the order of "billions" of birds killed every year by domestic cats.

The question isn't whether cats will hunt a bird or rodent, but to my thinking whether their impact is any greater than say the risk of birds running into windows, etc. Feels a bit like when we blame the cow for burping (IE: doing what it does naturally) as the cause of global warming while we continue to drive around in our carbon-belching cars.

View on HN

https://blogs.umass.edu/natsci397a-eross/the-environmental-a...

We've had 3 birds hit our windows in the 12 years I've owned this home. To combat that, I made sure all the windows had blinds. It hasn't happened since.

My one neighbor's cat kills more than 3 birds per month in the warm seasons. I haven't been able to combat that unfortunately.

But I did build a dry stack retaining wall that has allowed the chipmunk population to have a bit of refuge. They are slowly growing in numbers. We had scores of them until the neighbors moved in next door. Within months they dwindled to less than a dozen. My wife and I used to love to sit at our breakfast table and watch them scurry around the yard and patio. Our neighbor's cat ruined that for us.

I shouldn't have to spend $5k+ to prevent cats from killing chipmunks, but I'm always willing to do whatever I can to improve something rather than just complaining about it.

> We estimate that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3–22.3 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. 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.

https://www.nature.com/articles/ncomms2380

The thing I always wonder is, in habitats where birds would normally have to deal with feline predators, how is the domestic cat worse than that? Any birds in environments that have feline predators would already be adapted to avoidng cats, unlike say, small Australian fauna.

I can understand the damage inflicted by cats in environments that never had a very efficient bird predator like cats (e.g. New Zealand and other islands). But in North America there's the Bobcat, Lynx, Ocelot, Margay, and Jaguarundi. Even without the domestic cat, birds would still get eaten in sizable numbers by cats. Sure there are a lot more domestic cats out there, but without civilization there would be a lot more wildcats out there eating birds.

Maybe the impact is simply that outside house cats exist in numbers that are not supportable for a normal wild predator due to the fact that house cats have meals provided by humans to sustain them. So house cat numbers don't reach an equilibrium with their prey the way a wild cat could. Either way I suspect that the impact on bird populations by domestic cats is often overstated.

>Maybe the impact is simply that outside house cats exist in numbers that are not supportable for a normal wild predator due to the fact that house cats have meals provided by humans to sustain them. So house cat numbers don't reach an equilibrium with their prey the way a wild cat could.

That's exactly it. The density of house cats is orders of magnitude larger than the density of wildcats would be.

> Either way I suspect that the impact on bird populations by domestic cats is often overstated.

Why?

Last time I looked, which was a while ago, there were over 9 million cats in the UK. I suspect a similar number for the US, proportionally, so I can't see any way that the wildcat population could ever rise that high. Domestication brings safety and an ever increasing population, not just for humans.

https://abcbirds.org/article/study-documents-dramatic-new-im...

https://abcbirds.org/wp-content/uploads/2015/06/Medina-et-al...

https://abcbirds.org/wp-content/uploads/2015/09/Loss_et_al._...

https://abcbirds.org/wp-content/uploads/2020/09/Doherty-et-a...

The first result on Google for "how many birds are killed by domesticated cats" is a scientific article from the Smithsonian Conservation Biology Institute and the U.S. Fish and Wildlife Service.

https://www.nature.com/articles/ncomms2380

An article is as good as the data that supports the research.

We have to keep in mind that this is an article based in google search and bibliography and is just a very raw estimate. Bibliography studies mostly the worse and special cases. There is a risk into taking the worse cases as a sample of the global situation.

Is a guess, much better than having none, but still a guess. Don't overthink it

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