Is there isomorphy in eggs belonging to species of the family Ardeidae?
Egg shapes in birds reflect many anatomical, biophysical and ecological aspects. In previous literature it has been assumed that a similarity in volumetric indexes from external dimensions is an indicator of constancy in shape of egret eggs (Birds, Ardeidae), but results are not consistent. Previous researchers have used lineal dimension rates to estimate shape, but these can distort the results because both aspects are orthogonal by definition. In the current research we analyze differences in egg shape between eight species of egrets and herons using elliptic Fourier descriptors and landmarks over 203 digital pictures of eggs kept in oological collections. Comparison between species and a discriminate function analysis show that shape is insufficient to distinguish species. The elongation index and breadth of eggs were significantly correlated. Our results suggest that egg shape can discriminate ecological groups but not species, indicating there is no general isomorphy in Ardeidae.
Egg shape, Egrets, Herons, Fourier, Landmarks
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