If you read the article, they actually argue that the cats don't really have an effect because those 40 million birds are usually of species that aren't endange

If you read the article, they actually argue that the cats don't really have an effect because those 40 million birds are usually of species that aren't endangered and are usually birds that otherwise wouldn't have made it anyway. Though 40 million dead birds sounds like a lot, in regions where wildlife had millenia to adapt to cats' existence – in continental Europe cats have existed for tenthousands of years – it’s not a significant issue. And it's sad that so much time and energy is wasted on this discussion when people are still spraying their own backyards with pesticides and destroying "weeds", which are actually necessary for insects, and as result birds, to thrive.