U.S. scientists using sound have made a significant discovery that sheds new light on the wintering grounds of the Pacific humpback whale.

Researchers from the Hawaii Institute of Marine Biology and the National Oceanic and Atmospheric Administration said the primary humpback breeding ground for the North Pacific was always thought to be the main Hawaiian Islands. However, scientists recording whale songs have discovered these breeding grounds extend all the way throughout the Hawaiian Archipelago and into the Northwestern Hawaiian Islands, also known as the Leeward Islands, a chain of small islands and atolls stretching thousands of miles northwest from the island of Kauai.

An endangered species once near extinction, between 8,500 and 10,000 whales migrate to Hawaii each winter, while other humpback populations can be found in Taiwan, the Philippines, the Mariana Islands and Baja California.

These findings are incredibly important because they re-evaluate what is known about humpback whale migration and the importance of the Northwestern Hawaiian Islands to the population.