Asked by: Simon Harvey, via Twitter
All seabirds drink seawater – yet birds have less efficient kidneys than mammals, and so excess salt is even more toxic to them than to us. Seabirds cope with this by using specialised salt glands next to their eye sockets. These look like miniature kidneys and work in a similar way, pumping salt ions out of the bloodstream against the normal flow of osmosis. The extra-salty water drips down the side of their beak.