Hays Bald Eagles H17 Preening after a Rainstorm (Study) 2022 05 07 13 21 59 230

The uropygial gland, informally known as the preen gland or the oil gland, is a bilobed sebaceous gland possessed by the majority of birds used to distribute the gland's oil through the plumage by means of preening. It is located dorsally at the base of the tail
While preening, Eagles remove dust, dirt, and parasites from their feathers and align each feather in the optimum position relative to adjacent feathers and body shape.