A bird's wing span varies with the size of the bird and the length of the bird's actual wing.
It is advisable that a trombone player have long arms so that 7th position on the horn can be easily reached.
It is said that Franz Liszt, 19th century piano virtuoso, had a wide hand span as he played the piano. There are varying opinions on this. Some say he could reach a 12th interval on the white keys; others say just a 10th interval. Some say he had small hand just a wide stretch; some say he just didn't have much webbing between his fingers.
I have heard pianists say that many can not play some of Liszt's music because the expectations for the music he created were too "big" for most musicians' hands. That it was a physical hindrance, not a lack of ability to play his music.
Whatever the exact story is, this is the one thing that caused several students to stay after class today to check to how many keys their hands/fingers could reach.
Each one was eager to s-t-r-e-t-c-h his/her hand on the piano keys to see what they could reach.
(Most could reach the 10th-11th interval.)
Whatever the reason, about 10 students put their hands upon a piano today.
For some it was the first time ever.
Hopefully it won't be the last.