1. Kramer, G., Ibis, 99, 196 (1957).
2. Kramer, G., in “The Biology of Birds” (Academic Press, New York) (in the press).
3. Matthews, G. V. T., J. Exp. Biol., 30, 243 (1953).
4. Matthews, G. V. T., “Bird Navigation” (Cambridge, 1955).
5. Rawson, K., and A., J. f. Orn., 96, 168 (1955).