Studies and experiments have shown us that you can put a cat in its place simply by drawing a circle or a box on the floor. How much better is that box when it come with its own warmth? The box made when the sun shines through a window is perfect for cats, but it moves slowly as the earth rotates, and the cat has to keep moving to stay in the box. If a cat isn't paying close attention, another cat can claim that nice warm box.
This time lapse video condenses four hours of sunlight into four minutes. We see Abby claim the sunspot. Then Cleo wants some of that sun, too. She thinks that if she moves slowly enough, Abby won't notice. But Abby does notice. Once Cleo has the spot, she almost lets it get away from her, and Athena thinks she can take the sunspot. Surely, there's enough sunlight for two cats! But if they spend all day competing for the sunspot, it will eventually go away. A good time was had by all.
And if you can handle it, here's a sad but touching story about two cats in a sunbeam from Jenny Jinya that I found within an hour of watching this video. You've been warned.