Tell My Name Now!!!

Joe, a college student, was taking a course in ornithology, the study of birds. The night before the biggest test of the semester, Joe spent all night studying. He had the textbook nearly memorized. He knew his class notes backward and forward. Joe was ready.
The morning of the test, Joe entered the auditorium and took a seat in the front row. On the table in the front was a row of ten stuffed birds. Each bird had a sack covering its body, and only the legs were showing. When class started, the professor announced that the students were to identify each bird by looking at its legs and give its common name, species, habitat, mating habits, etc.
Joe looked at each of the birds' legs. They all looked the same to him. He started to get angry. He had stayed up all night studying for this test and now he had to identify birds by their LEGS? The more he thought about the situation, the angrier he got.
Finally he reached his boiling point. He stood up, marched up to the professor's desk, crumpled up his exam paper and threw it on the desk. "What a ridiculous test!" he told the prof. "How could anyone tell the difference between these birds by looking at their legs? This exam is the biggest rip-off I've ever seen!"
With that, Joe turned and stormed toward the exit. The professor was a bit shocked, and it took him a moment to regain his composure. Then, just as Joe was about to walk out the door, the prof shouted out, "Wait a minute, young man, what's your name?"
Joe turned around, pulled up his pant legs and hollered, "You tell me, prof! You tell me!"