Two girls in Ireland take a trip on a canoe down the River Shannon. What they experience next is a rare occurrence in nature that we never would have expected.

According to Irish Central, these girls are Sophie Windsor Clive and Liberty Smith. Their trip down the River Shannon let them witness a phenomenon known as a "murmuration." Now, this term is typically used to describe a flock of birds called starlings. But it also describes the starlings' actions within the flock.

If you'll notice in the video, the starlings seem to fill up the sky and weave around, as if they made up a giant flag that floated in the air. This behavior in the murmuration is a survival tactic and serves the purpose of separating the weaklings from those more outfitted for surviving against predators. Because of their size, starlings are tasty snacks for bigger birds like peregrines and sparrowhawks. By flitting around rapidly in the air, they can judge who's best suited for survival, since the slower starlings are more likely to be caught by a predator.

It's been said that murmurations can approach speeds of 20 mph in the air, making it a literal race for survival. It's a wonder to see them mimic each other's movements and try to stay as close to the rest of the flock as possible.

Watch the video of the murmuration above and stare in awe at the rippling effects in the sky, knowing that they're birds.