Thickness histograms of Holocene fossil eggshell fragments indicate diversity and relative abundance of moas (Aves: Dinornithiformes) at North Island sites

Abstract

ABSTRACT Moa eggshell fragments from 13 North Island sites (New Zealand), were 0.54–1.74 mm thick (n = 6036). Thicknesses with published DNA-identifications overlapped greatly between the four North Island species, but median thicknesses were separate: Pachyornis geranoides thinnest, Dinornis novaezealandiae thickest, and Euryapteryx curtus and Anomalopteryx didiformis in the middle, but with the former slightly thinner. Thickness histograms for regional samples of unidentified moa eggshell fragments, each had one of four thickness patterns: Type A (thin eggshell only), Type B (thick eggshell only), Type C (medium-thickness eggshell only), and Type D (all thicknesses present). The Gisborne site, poorly-known from moa bones, had a similar thickness profile (Type D, skewed towards thin shell) to North Cape and Tokerau Beach implying a similar moa fauna. Eggshell thicknesses suggested that D. novaezealandiae was absent at Port Jackson (Type A histogram) and that P. geranoides was absent at Whananaki (Type B pattern) and rare at Herbertville (Type D, skewed towards thick shell). Thickness analysis for eggshell from a Lake Taupo archaeological site suggested that few eggs of just one species were involved, whereas a wide spread of shell thicknesses for a Great Mercury Island site implied a contribution from several species.