moustachial
/məˈstɑːʃɪəl/(also mustachial) Chiefly Ornithology
adjective
Resembling a moustache; specifically designating a streak of colour running back from the sides of a bird's beak.
Origin
Late 19th century; earliest use found in Edward Blyth (1810–1873), zoologist. From moustache + -ial.