Seagulls

My wife and I just returned from Cape May, NJ. The weather was great and we enjoyed a wonderful time together. Something occurred to me. Why does every seagull sound the same? Perhaps to the birder (of which I cannot be counted), each seagull has a distinct and beautiful sound. But to me, they all sound the same. They don't all look the same. It stands to reason that one would have a very deep voice and one would have a loud voice, one would have an accent...you see where this is going.