An analysis of the distribution and relative abundance of moa species (Aves: Dinornithiformes)

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Abstract
Contributions to the understanding of moa ecology are reviewed. The distribution and relative abundance of each moa species in natural and archaeological sites is examined in detail. Eleven moa species (three dinomithids and eight emeids) are recognised in this study. The three dinomithids each had a New Zealand wide distribution. Dinornis giganteus primarily had a lowland distribution that coincided with areas suggested to have been vegetated in open low forest or shrubland. It was rare in wet, dense tall forests where the medium sized D. novaezealandiae was the dominant dinornithid. D. struthoides, the smallest dinomithid, ranged from lowlands to subalpine areas and was most abundant in forested areas. Among the emeids Anomalopteryx didiformis and Euryapteryx geranoides had a New Zealand wide distribution, Euryapteryx curtus and Pachyornis mappini were North Island endemics, and Pachyornis australis, P. elephantopus, Emeus crassus, and Megalapteryx didinus South Island endemics. Anomalopteryx didiformis was primarily an inhabitant of wet lowland, tall podocarp-broadleaf forests. Both Euryapteryx species and Emeus crassus were lowland inhabitants of shrubland or open low forests, and thus predominated in drier regions. Euryapteryx curtus and Emeus crassus may have been ecological equivalents. In the South Island Euryapteryx geranoides seems to have preferred areas postulated to have been clothed in dry inland low forests generally over 200 m above sea level. Emeus seems to have had a predominantly coastal distribution. Megalapteryx didinus primarily inhabited upland areas of montane to subalpine habitats. Pachyornis mappini was a lowland species with an affinity for wetlands. It was rare in areas of continuous tall forest and most common where a shrubland-forest mosaic existed. P. elephantopus was the South Island equivalent of P. mappini but was absent from continuous areas of wet tall forests. P. australis replaced P. elephantopus in montane forests and subalpine areas, apparently preferring wetter colder areas. This analysis shows patterns of distribution that are correlated with differing vegetation types so allowing general habitat preferences to be determined. Each species clearly had a distinctive habitat preference that suggests that usually only three to four species coexisted in any one habitat, niche separation being effected by differing sizes and beak morphologies. It is no longer acceptable to refer to moa ecology without qualification by taxa concerned.