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

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.

KEYWORDS:

• Moas
• Dinornithiformes
• New Zealand
• fossil eggshell
• shell thickness
• geographic variation

Acknowledgements

I thank Louise Furey and Emma Ash (archaeology collection, AIM) and Alan Tennyson (bird collection, NMNZ) for access to eggshell samples in their care. Clint Easton informed me of eggshell (at NMNZ) he had collected at Martinborough Caves, and Mark Speedy allowed access to his Herbertville property; both helped collect eggshell at Herbertville. I thank Leon Huynen and David Lambert for sharing DNA identifications obtained from moa eggshell in the AIM collection, and Trevor Worthy for critical comments on a draft of this paper.

Disclosure statement

No potential conflict of interest was reported by the author.