Shapes of Birds' Eggs: Extant North American Families

Abstract

The shapes of birds' eggs, as distinct from their sizes, can be very closely specified by three parameters, elongation, asymmetry, and bicone, as used in the Handbook of North American birds (Palmer, 1962). The present paper shows that they cannot be specified by less than three because no significant correlation exists between any two of the three. The distribution of any one of the parameters is not normal or Gaussian, and strongly suggests that there must have been now-extinct families with intermediate properties. Existing reptiles considerably extend the range of some parameters beyond those of birds. Negative bicone, however, seems to be essentially an avian monopoly and its function is not clear. The properties of Monotremes' eggs are inadequately known.