True: Though we hope your Easter Eggs are not painted this way! Hoopoes actually paint their eggs with a smelly, brown fluid produced from a gland near their rear ends. Birds normally use the oils secreted by this uropygial gland to preen their feathers, but hoopoes are unique in that their uropygial secretions are full of bacteria. Unlike other birds' eggs the shells of hoopoe eggs are not smooth and are covered in tiny pits. They smear the pitted surfaces of their eggs with this microbial 'paint', and researchers have found that this actually reduces the amount of harmful bacteria inside the eggs, with the friendly bacteria acting as a sort of shield for the developing chicks.