Do temporal size differences influence species identification of archaeological albatross remains when using modern reference samples?

Zooarchaeological remains have been identified to species, using identification criteria based on specific morphological variations among modern specimens. However, temporal size changes in bones, due to micro-evolution and/or phenotypic plasticity, could distort identification of archaeological remains according to these criteria. We developed species identification criteria for North Pacific albatrosses (Short-tailed, Laysan and Black-footed Albatrosses) using both mensural- and DNA-based analysis and actually identified many archaeological remains from a site using these criteria. Our mensural-based criteria could accurately discriminate the modern Short-tailed Albatross from modern Laysan and Black-footed Albatrosses and indicated that the archaeological remains included both Short-tailed and Laysan or Black-footed Albatrosses. DNA-based criteria, however, suggested that all remains were Short-tailed Albatross. The most plausible explanation for this inconsistency would be misidentification using mensural-based analysis, due to temporal size changes in bones or existence of birds from extinct population(s) or breeding region(s) with mensurally different bones from recent birds. This is the first study that suggests temporal size changes in bones may distort the species identification of archaeological remains according to modern size variations. Further studies are required to judge if this pattern is unusual or not.