Every winter, monarch butterflies fly thousands of miles from the US and Canada where they breed, all the way down to the forests of central Mexico where they wait out the cold before heading back home in the spring.

While this phenomenon by itself is one of the most impressive things in the natural world, something incredible also happens once they arrive at their sun-abundant destination in the south — the magnificent sound of millions of monarch butterflies flapping their wings together.

As documented by nature host Phil Torres of The Jungle Diaries, as the butterflies reach their warm destination, they cluster together on trees in order to stay warm, covering entire branches and leaves in thick butterfly blankets. As the sun warms up the insects, the colorful creatures take flight all at once. Torres calls this collective movement a “waterfall” because the sound of the flapping wings resembles the soothing tones of falling water.

Though not as endangered as other butterfly species, monarchs are increasingly threatened by pesticides, climate change, urban sprawl, and deforestation. They only eat milkweed, a plant that has been devastated by increased herbicide spraying and other chemicals toxic to the young caterpillars. As such, people can help boost this species’ resilience by planting milkweed and native flowering plants, which is their primary habitat.

To watch the breathtaking moment millions of monarch butterflies take flight and make one of the most exceptional sounds on earth, click here.