Sumner, E. L., Jr.
1929a. Notes on the growth and behavior of young Golden Eagles. Auk, 46:161-169.
1929b. Comparative studies in the growth of young raptores. Condor, 31:85-111.
1933. The growth of some young raptorial birds. Univ. California Publ. Zoöl., 40:277-307.
1934. The behavior of some young raptorial birds. Univ. California Publ. Zoöl., 40:331-361.
Fig. 3. Young Great Horned Owls in nest. Two owls are 7, 12, 18, 32, and 36 days of age, respectively; the third owl is about 2 days younger in each instance.