Swans produce tears to cleanse their eyes just like humans. However, sometimes the tears are due to stress (overheated) or from water that has not repelled from the beak area. The swans will fling the excess water from their beaks and heads.

Additionally, the swans are rubbing their heads all over their feathers for some very important reasons. First, the swan has an uropygial oil gland (preen gland) near its rump. The oil from the preen gland is believed to serve several purposes such as making the feathers water repellent, keeping the feathers healthy by providing possible antibiotic traits (although various conflicting studies have been conducted regarding this issue), and it is believed that the oil provides an ultraviolet trait to the swans' eyes which allow it to distinguish and recognize other swans as well as maintain the health of the eyes.

The swan will rub its head and neck along the uropygial gland area thereby coating the head and neck with the oil. Then, the swans will rub their head and neck over their bodies to add oil to their overall feathers. The swans will then zip their feathers similar to velcro so further clean, tidy and make the feathers water repellent and ready to fly if the birds are capable of flying. Most waterfowl have the uropygial oil gland and will perform the same feather cleaning and tidying as swans. The Regal Swan
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