A. Skutch, 1935, _Auk_, 52, p. 257 (helpers at nest). M. M. Nice, 1943, _Trans. Linn. Soc._, Vol. 6, p. 79 (young feeding young). R. C. Murphy, 1936, _Oceanic Birds of South America_, Vol. 1, p. 360 (emperor penguins).