Gloydius shedaoensis

The Shedao Island Pit Viper is a grey-brown snake marked with a series of dark, X-shaped dorsal patterns and a narrow dark stripe behind the eye. Adults average approximately 65–70cm from snout to vent. The species occurs only on tiny Shedao Island off Liaoning in northeastern China. (Wikipedia, general species account)

Its ecology is closely tied to migratory passerine birds that visit the island in spring and autumn. The vipers ambush birds either on the ground or from branches, holding the front of the body in a folded striking posture. During the remainder of the year, when migrating prey is unavailable, the snakes undergo prolonged inactivity. (Wikipedia, general species account)