The diets of moa (Aves: Dinornithiformes)

For tens of millions of years the ratite moa (Aves: Dinornithiformes) were the largest herbivores in New Zealand’s terrestrial ecosystems. In occupying this ecological niche for such a long time, moa undoubtedly had a strong influence on the evolution of New Zealand’s flora and played important functional roles within ecosystems. The extinction of moa in the 15th century ce therefore marked a significant event in New Zealand’s biological history, not only in terms of biodiversity loss, but in the loss of an evolutionarily and ecologically distinct order of birds. Understanding the full extent and magnitude of this loss, and its implications for New Zealand ecosystems, depends upon a detailed knowledge of moa diets. Over the past 100 years, periodic discoveries of preserved moa gizzard content and coprolites (ancient preserved dung) have gradually begun to shed light on the diets of moa and their roles within New Zealand ecosystems. Here, we review how the study of such samples has shaped our understanding of moa diets through time. We then provide a synthesis of current knowledge about moa diets, including summarising 2755 records of plant remains from 23 moa gizzard contents and 158 moa coprolites. A clear picture is now emerging of distinct differences between the feeding ecologies of moa species, which together with differences in habitat preferences facilitated niche partitioning. Such insights provide empirical data to inform the debate surrounding the role of moa herbivory in the evolution of distinctive plant traits within the New Zealand flora. These data also help identify specific ecological functions and roles that have been lost due to the extinction of moa, and resolve to what extent these could be replaced via surrogate taxa.