The identification of bird eggshell by scanning electron microscopy

Archaeologists and ecologists have increasingly developed new tools to help us understand the character of past ecosystems as well as human influences upon them. This study advances a refined method for the identification of avian eggshell fragments recovered through archaeological, ecological, and paleoecological fieldwork. The method is based upon high-resolution scanning electron microscopic (SEM) imaging of the inner surface of the eggshell and a system to describe the diagnostic features. These include the shape and texture of mammillae (the protruding ends of the calcareous columns that make up most of the eggshell) and the microrelief of intermammillary spaces and contact points. We also propose a method to measure the spatial density of mammillae. Finally, we provide a visual reference collection of eggshell from 25 bird species, most of which are widespread in the North Atlantic region, where our research is focused. By focusing upon one taxonomic group in particular (ducks, 10 species) we affirm that eggshell microstructure is species specific. This methodology is easily transportable to other regions and species assemblages and we advocate cataloging eggshell micromorphology on a larger scale to facilitate the use of eggshell fragments in archaeological and ecological studies.