Seagulls usually have red mouths. This is because seagulls have abundant blood supply in their mouths, and hemoglobin in their oral tissues will make them appear red. This color is more obvious in adult seagulls, while the beaks of young birds are lighter red or black. The color of seagulls' mouths helps them convey visual signals when courting, deterring enemies and engaging in social behavior. The color of the mouth may also change due to the species and individual differences of seagulls, but red is one of the most common colors.