The Collaborative International Dictionary of English v.0.48:

Sleepyhead \Sleep"y*head`\, n.
   1. A sleepy person.
      [1913 Webster]

            To bed, to bed, says Sleepyhead.      --Mother
                                                  Goose.
      [1913 Webster]

   2. (Zool.) The ruddy duck.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sleepyhead
    n 1: a sleepy person