A thousand years ago, gigantic 12-foot-tall flightless birds roamed New Zealand, snacking peacefully on plants and fungi. Then humans came along. Within two hundred years, the giant moa—along with a host of their close cousins—were dead at our species’ hands.

What did the world of the moa look like? Even though New Zealand has lots of well-preserved wilderness, studying that won’t give us an answer. When a species disappears, it takes a chunk of its ecosystem with it, so understanding the ramifications of the moa extinction can help us better understand the environment that many surviving species—some of them critically endangered—evolved in.

Some important answers lie in something the moa left behind: ancient bird poop. It tells us that the moa were probably instrumental in spreading the fungi that play a critical role in New Zealand’s forests.