Birds of a feather

… flock together, but moa thrived by being different.

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Attard Et Al

Differences in the shape and dimension of beaks allowed nine species of moa—one of the biggest birds in the world—to roam New Zealand’s forests, grasslands and coasts without squabbling over food, according to research published in Proceedings of the Royal Society B.

The coexistence of up to six species of moa in one place was originally thought to be a function of body size (which ranged from 20 kilograms to 200 kilograms) that would give them access to different flowers, fruits, leaves, shoots and branches of shrubs and trees that are seen in fossilised moa dung.

However, scientists from New Zealand and Australia used medical CT scanners and MRI on the mummified skulls of five different moa to determine how the muscles joined with the beak, indicating the strength and range of movement they were designed for.

They found huge biomechanical differences. Some species, such as the coastal moa, had very weak skulls and beaks with rounded flattened tips that could cope only with munching soft fleshy fruit and leaves, a diet much more limited than originally thought, which could explain why they needed to roam further. Others, such as the little bush moa, could powerfully shear fibrous twigs off branches with the sharp edges of their shortened beaks and pull back hard. Of all examined in the study, the upland moa appeared best suited to tearing out vegetation, while the South Island giant moa was better adapted to shake vegetation from the earth side-to-side.

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