Using measurements to predict laying order in harvested Northern Rockhopper Penguin (Eudyptes moseleyi) eggs

The sustainable and responsible exploitation of natural populations for subsistence requires a scientific basis for management. Eggs of the Endangered Northern Rockhopper Penguin (Eudyptes moseleyi) in the Tristan da Cunha archipelago have been harvested since the 19th century with no restrictions on which (A- or B-eggs) can be harvested, despite the larger B-egg being much more likely to produce fledged offspring. Our objective was to create a discriminant function to predict the laying order of harvested eggs. We found that the discriminant function of D = 0.58 x Length + 0.39 x Breadth -57.48 successfully classified 91% of eggs as A- or B-eggs. When applied to previously collected harvest data, the discriminant function identified at least 36% of eggs as B-eggs. The method we describe here provides a mechanism around which one aspect of a management framework for the sustainable harvest of Northern Rockhopper Penguin eggs can be built.