Oil gland in birds is present at the ____X_____ and helps in ____Y_____. X and Y are

	X	Y
1.	base of the wings	gliding through the air
2.	base of the tail	water-proofing
3.	base of the wings	preening of the feathers
4.	base of the tail	excretion of the wastes

In birds, skin is dry without glands except the oil gland at the base of the tail. The oil from each lobe of the gland is secreted through small papilla (nipple-like projection). It performs many functions in the bird including water-proofing, and keeping the skin, feathers and bill supple. The oil is said to have some antibacterial function.