Birds eliminate their waste as urea.

The excretory system helps in the removal of the nitrogenous wastes from the body of the organism into the external environment. The form of nitrogenous waste that is being removed can vary based on the organism's habitat. In the case of birds, the nitrogenous waste that is removed from their body occurs in the form of uric acid. Birds release uric acid in the form of a white paste.  Their waste material is removed through a single orifice called the cloaca.  The cloaca is a common pathway for the removal of waste material and is also used for egg-laying.