One thing not factored into the cat numbers is how many birds would be killed in a non-suburban, non-house cat habitat anyway. That is, birds are preyed upon by bobcats, other birds, snakes and such. House cats are replacing these apex predators in suburban environments.

Interestingly, I worked for (landscaping) almost 40 years in a neighborhood in Irvine,CA. Many people had outdoor cats and there did not seem to be a noticable deficit of birds (though that's a guess). In the early 90s coyotes moved in and starting on preying cats so everybody brought their pets indoors. The rabbit and rat populations subsequently exploded! I would see hundreds of rabbits mowing down people's lawns in the morning drive to the site. Residents could not grow veggies or fruit because rats would eat them ( A pair of bobcats did take up residence for awhile and controlled the problem but they were killed by rat poison put out by folks). Interestingly the coyotes could never control the varmint problem--in direct opposition to local environmentalist theory.

Anyway, you would think with this dearth of outdoor cats the bird populations would flourish...not so! It is just a relatively barren avian ecosystem with the usual suburban denizen-- lots of crows,a few pigeons, mockingbirds, and a few finches. Why is this? It's probably because the crows and rats are eating nestlings and eggs of more diverse species!

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Great article 👏 Thanks.

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To be thorough, humans directly slaughter orders of magnitudes more birds each year. Completely understandable that Hannah doesn't discuss the factory farming of chickens and turkeys, as she has her lane where she's making such a big difference. But the brutality of today's chicken factory farms and industrial slaughterhouses absolutely dwarfs everything else in the developed world.

This is not, BTW, a "Go Vegan!!!" comment. Just noting that in suffering per plate, chicken is the worst choice. https://www.onestepforanimals.org/about.html

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I think it would be helpful to have a conclusion about whether wind farms are net positive for birds and bats compared to alternatives.

There are also some studies - to be treated carefully, as they are produced by turbine manufacturers - that suggest that offshore wind is not a major problem for birds. For example: https://group.vattenfall.com/press-and-media/newsroom/2023/unique-study-birds-avoid-wind-turbine-blades

An early study with input from the RSPB, Natural England and UK government: https://www.carbontrust.com/news-and-insights/news/pioneering-study-finds-seabirds-avoid-offshore-wind-turbines-much-more-than-previously-predicted?utm_source=dlvr.it&utm_medium=twitter

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Another idea would be to establish an environmental ceiling on how many birds a given turbine can kill. Once the number is exceeded, the turbine stops for a designated time...even at the expense of the operator and/or consumer.

I'm reminded of how the US Department of Agriculture has been actively trying to kill birds to protect sunflower crops for decades...


...populations kept rebounding. They continue to search for ways to limit their damage. But bats don't breed as quickly as say Blackbirds, so rebounds are difficult if not impossible.

On solutions, I know it antithetical for mainstream economists to call for limits that may 'eat into profits', but at some point isn't profit of capital over profit of life a bit anti-ethical?

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This was very interesting, but I was confused by two sections. First, in your table of estimates, one column is "deaths per GWh per year", which I can't get my head round. That implies deaths would scale with power, not with energy production. Surely if you run a turbine for 2x as long, producing twice as much energy (but at the same power output), it'll kill 2x as many birds, not the same amount (all else equal)? Further discussions all seem to be in deaths per unit energy, not power, so is this just a typo-type error?

Second, when discussing the breakdown of deaths attributed to fossil fuels, the breakdown is by GWh, but surely this must mean by *deaths per* GWh?

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Hannah, interesting article.

Given the rapid increase in size, there are some issues with scaling up "birds strikes per turbine", to the total TWH produced in the US.

As you show later, smaller turbines have more strikes per turbine, but a large proportion of the annual energy produced will come from the bigger turbines, albeit many fewer of them. I'm not sure if this would increase, or decrease the overall number - but the trends are very clear, smaller, older turbines are getting to the ends of their economic lives and being replaced by much larger modern turbines. (admittedly this is all a bit academic as the message is the same - it's not exactly worth worrying about, we could just cull 10% of cats and that would have a much bigger impact - just don't tell my cat that!)

Also, for bats, there are detection systems that can scan the area in front of the turbine and shut down if significant bats are in the area, it doesn't usually harm production much as it's lower wind periods in the dawn and dusk (maybe 2 hours a day if I remember correctly).

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Dear Hannah,

Please correct me if I am wrong, but I beleive your message about wind farms killing birds only relates to Horizontal Axis Wind Turbines (HAWT) not Veritical (VAWT). I personally do not believe that HAWTs is the Wind Farm of the future, VAWTs make much more sense and one reason is that far less birds are filled by them, if almost any.

If you really want to complete this bird killing discussion....you should look into VAWTs.

And there are other reasons why those HUGE HAWTs are just the result of lazy engineers and scientists, who did not look into VAWTS long enough to make a education choice - of of which is the waste they are producing from HAWTs that fall apart, explode, etc.

You might want to check the tables/charts I put in my first post on the subject of VAWTs.


May I use some of your information in my next VAWT post?



Wishing to encourage Everyone to find the Value in their Waste.

https://wasterush.info/ fossil fuel is ancient Waste. We can do better with today's Waste.

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great article, super balanced approach to the issue. I love how you interrogated every assumption.

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The Sovacool bird study is so non-scientific and nonsensical that it is so not cool, and should be denounced more strongly.

He assumes a large percentage of bird species will go extinct because of warming, for which there is no evidence of, and then extrapolates that if X% of species go extinct then that same number of birds will die. There are 50 billion birds on earth and more than 10% are sparrows, starlings, gulls and swallows. If the ivory-billed woodpecker becomes extinct (0-10 individuals currently suspected to exist) it won’t have a noticeable effect on the total bird population. Any species threatened with extinction necessarily has few individuals, white rhinos going extinct would be a loss, but won’t change the number of large mammals in Africa. His nuclear study is even worse as the rebuttal you linked to states (a barely operating mine in Colorado once had a kerosene spill which killed 40 Canadian Geese (a much disliked bird) in a one-time accident and he extrapolated that to be per kilogram of uranium produced over all years at all locations as though it was caused by the actual amount of uranium mined.

By giving any respect to these kind of ridiculous and biases studies does not increase my confidence in any other statistics you state, and I don’t want anyone to question he quality of ourworldindata statistics, which are too important to tarnish with bad data.

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Thank you for putting this problem in context, Hannah. It's often very difficult to see the counterfactual of what a technology would replace (both good and bad), so looking at the numbers here for wind power was helpful for me.

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Oh God. Nit this again. Cats kill about 2 billions birds a year. In North America alone!

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They cost more to run than use. Cost more to the land owner than anyone. No easy way to recycle them. They are a criminal enterprise sell out to the UN Elite

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Having commented earlier, it is encouraging to see that the wind industry can behave responsibly. Another point of differentiation from the fossil fuel sector. This in today's news (Denmark cancels planned offshore wind project as area is redesignated as a bird sanctuary). https://reneweconomy.com.au/danish-offshore-wind-project-cancelled-after-area-redignated-as-bird-sanctuary/

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thank you so much for your careful and considered work on these issues Hannah; fascinating and important in equal measure! _/\_

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