My impression is that this bird is a magpie and she is defending her young. I’m not an ornithologist so I am assessing what’s happened as a layperson (update: the magpie is attacking the cat during nesting season). The cat, which looks like a dilute ginger tabby, simply wandered onto the bird’s territory. That is the way I see it. A totally innocent act by the cat. The bird was very brave, obviously, to have a pop at the domestic cat because she paid a price, the ultimate price as you can see when the cat makes a mighty leap as the bird flies away. The cat captures the bird in her jaws and that is the end of the bird. What I find so impressive is that this short-animated gift (short, repeating video based on still images) demonstrates to us and reminds us that the domestic cat retains its wild ancestor’s abilities through long levers and fast twitch muscles. This is a leap from a standing start which makes it all the more impressive.