Humans aren’t the only animals that fall in love. In fact, as much as 70 percent of birds may form long-term pair bonds. That is, they stay together year after year. Or in some cases, they split up, then come back together when it’s mating season. And every year, the pair, or just the male, performs a fancy mating dance. Trevor Price, a biologist at the University of Chicago, has long wondered why they do it.

You can see some of these dances on YouTube. In the Andes Mountains in South America, water birds called hooded grebes have bright red eyes. They have spiky ruffles around their heads that make them look like Dr. Seuss characters. They perform complicated tangos in lakes.

Scientists weren’t sure for a long time what purpose the mating dances served.

That’s because some of these birds may have gotten together last season, says Price. They’ve already successfully had babies together. They don’t need to attract each other anymore.

“It’s such an obvious question,” he says. “Why bother with the dance when you could just get on with raising your brood?”

He thinks he may have found an answer. Perhaps 1 million years ago or more, a male grebe needed bright colors and tricky moves. He evolved to have them so he could convince a female that he was Mr. Right. His colors and dances raised her hormone levels. This caused her to lay extra eggs. It also may have made her work extra hard to take care of their babies, even to the point of exhaustion.

Over many generations, though, male grebes started to look less dazzling. Their partners figured out how many eggs to lay, so they didn’t have to work too hard. But the flashy mating behavior stayed the same. Explains Price, “If a guy brings home 12 roses every day, and on the 10th day he doesn’t, that might [upset] his wife.” So the birds are stuck forever in their mating rituals.

This is true for zebra finches, waved albatrosses, tropic birds and juncos, too. If you look out your window, you might catch common cardinals feeding and singing to their partners to make them happy. Humans “have a sense of well-being” from our relationships, says Price. “And animals do, too.”

Bird couples can split up, Price says. “But there are tremendous advantages to not getting divorced. A [familiar] mate can hit all the right buttons.” One study separated canary couples for the winter. When the birds got back together, they bred a whole month earlier than usual.

It’s no secret that birds are endangered everywhere in the world. At least 800 million of them die every year by accidentally hitting windows, Price says. The same number die from attacks by house cats. Price hopes that if people can understand that birds, like humans, feel emotions, they will care more about their survival. “There are a lot of things you see in your backyard that look like love,” he says. You can help that love continue by keeping your kitties inside.