Fulmars are tubenoses, and like other Procellariiformes they store a waxy, energy-dense stomach oil derived from their prey. In adults the oil is chiefly a compact food store, fed to a chick that a parent may reach only after a long foraging trip. In defence it becomes a weapon.
A threatened bird, and particularly an unguarded chick, ejects the oil forcefully and accurately over a distance of a metre or more. On a mammal it is merely rank and persistent. On a bird it is dangerous, because the oil destroys the structure of feathers that keeps a seabird waterproof and buoyant; raptors and gulls that have been sprayed have been found dead or unable to fly. The name comes from Old Norse for foul gull.
The fulmar is often taken for a gull on the strength of its colouring, but the tube on the bill and the stiff, banking flight place it with the petrels. A separate and well-established use of fulmars is as a plastic pollution monitor in the North Sea, since beached birds' stomach contents are systematically sampled.