WASHINGTON (AP) — Nearly half of the world’s migratory species are in decline, according to a new United Nations report released Monday.

Many songbirds, sea turtles, whales, sharks and other migratory animals move to different environments with changing seasons and are imperiled by habitat loss, illegal hunting and fishing, pollution and climate change.

About 44% of migratory species worldwide are declining in population, the report found. More than a fifth of the nearly 1,200 species monitored by the U.N. are threatened with extinction.

“These are species that move around the globe. They move to feed and breed and also need stopover sites along the way,” said Kelly Malsch, lead author of the report released at a U.N. wildlife conference in Samarkand, Uzbekistan.

Habitat loss or other threats at any point in their journey can lead to dwindling populations.