Sustenance is so hard to come by in North Korea that the region's vultures no longer bother to stop on their annual migrations in search of a meal.

Scientists from South Korea's Ecology Environment Institute have been monitoring the birds' winter migratory routes for five years, the JoongAng Daily reported, and have learned that the vultures stock up in north-east China before attempting the transit of North Korea to the relatively plentiful feeding grounds in the southern reaches of the peninsula.

"This seems to happen because in North Korea the vultures can barely find animal corpses, which are major food resources for them", Lee Han-su, the head of the institute, said.