Cordelia

It's not 100% clear, but it sounds like the study the video cites had domestic and other cats as part of the meso-mammal group. Which in this study was the 3rd largest predator group. It also might be worth noting that this study seemed to focus only on predation of eggs and nestlings. It's possible that cats tend to eat birds when they're older. A lot of domestic cats aren't great when it comes to getting up and down trees. I don't have any data for this, but it would makes sense to me if most of the birds cats are eating are older/ out of the nest. As for numbers, according to an article on this site cats apparently kill an estimated 1.4 to 3.7 billion birds in the US annually. And of course even a well fed cat will often kill birds out of instinct. So definitely a problem. I'm a cat lover too though. I usually just remind people that keeping cats indoors also allows cats to live longer, and that if they're worried about enrichment a "catio" can be a great option. For an established outdoor cat I'd encourage people to consider a bright reflective collar with a bell. It gives birds at least some warning, and can also help protect their cat from cars