Moa: The Giant Extinct Birds of New Zealand

The moa were a group of flightless birds that once dominated the landscapes of New Zealand. Belonging to the order Dinornithiformes, these birds evolved into a variety of forms, ranging from smaller forest dwellers to the colossal giant moa. As ratites—a group of flightless birds that includes ostriches and emus—moa occupied the ecological niches typically held by large mammals in other parts of the world.

Their existence spanned from the Miocene epoch through to the Holocene, roughly 17 million to 6,000 years ago. These birds are a classic example of island gigantism, where isolated species evolve to much larger sizes than their mainland ancestors due to a lack of competition and predators.

Size comparison between four moa species and a 1.8 m tall human. From left to right: Megalapteryx didinus, Dinornis robustus (female size), Anomalopteryx didiformis, and Pachyornis elephantopus

Key Facts

Diversity: Comprised 6 genera and 9 recognized species.
Range: Endemic to the North and South Islands of New Zealand.
Classification: Part of the Palaeognathae infraclass (ratites).
Temporal Range: Existed from the Miocene to the Holocene (17–0.0006 Ma).
Distinctive Feature: Completely flightless with no wing remnants.

Classification and Diversity

The moa are categorized into three primary families, each representing different sizes and habitats. The Dinornithidae family contained the giant moa, while the Emeidae and Megalapterygidae families consisted of smaller, more specialized species.

The Giant Moa (Dinornithidae)

The genus Dinornis included the largest of all moa. This group is split into the North Island giant moa (Dinornis novaezealandiae) and the South Island giant moa (Dinornis robustus). These birds exhibited extreme reversed sexual size dimorphism, meaning the females were significantly larger than the males.

A restoration of Dinornis robustus and Pachyornis elephantopus, both from the South Island

The Lesser Moa (Emeidae)

This family was more diverse, including several genera that adapted to various environments:

Anomalopteryx: The bush moa (A. didiformis), found on both islands.
Emeus: The eastern moa (E. crassus), native to the South Island.
Euryapteryx: The broad-billed moa (E. curtus), found on both islands.
Pachyornis: This genus included the heavy-footed moa (P. elephantopus), Mantell's moa (P. geranoides), and the crested moa (P. australis).

Model of a juvenile coastal moa (Euryapteryx curtus)

The Upland Moa (Megalapterygidae)

The upland moa (Megalapteryx didinus) was specialized for the higher altitudes of the South Island. Unlike the giant moa, these birds were smaller and adapted for more rugged terrain.

Physical Characteristics and Biology

Moa were characterized by their powerful legs and lack of wings. While other ratites have vestigial wing bones, moa are unique in that they had no wing elements at all. Their skeletal structures varied by species, with the giant moa possessing massive frames to support their weight.

The skeletons of an eastern moa (l), ostrich (rear), and Fiordland penguin (r) in the Otago Museum

Reproduction and Growth

Research into moa eggs and embryos reveals unique nesting behaviors. Some species produced eggs that were exceptionally large relative to their body size. Evidence from the Otago Museum shows female upland moa with eggs in an unlaid position within the pelvic cavity, providing insight into their reproductive anatomy.

An egg and embryo fragments of Emeus crassus

The skeleton of a female upland moa with egg in unlaid position within the pelvic cavity in the Otago Museum

Diet and Ecology

Moa were herbivores, browsing on a variety of New Zealand flora. Their diet varied by species and habitat, with some preferring the dense bush and others the open uplands. Their footprints, preserved in various sites, provide evidence of their movement and distribution across the islands.

Preserved footprints of a D. novaezealandiae found in 1911

Interaction with Predators and Humans

Before the arrival of humans, the primary predator of the moa was the Haast's eagle, a massive raptor capable of attacking moa pairs. However, the arrival of humans led to a rapid decline in moa populations due to hunting.

Early human settlers relied on moa as a primary food source. Historical reconstructions and illustrations of moa hunts depict the scale of these birds and the methods used to capture them.

An early 20th-century reconstruction of a moa hunt

Moa Summary Table

Overview of Major Moa Genera
Genus	Common Name	Distribution	Family
Dinornis	Giant Moa	North & South Islands	Dinornithidae
Anomalopteryx	Bush Moa	North & South Islands	Emeidae
Emeus	Eastern Moa	South Island	Emeidae
Pachyornis	Heavy-footed/Crested Moa	North & South Islands	Emeidae
Megalapteryx	Upland Moa	South Island	Megalapterygidae

Frequently Asked Questions

Why did the moa go extinct?

The moa went extinct primarily due to hunting by early human settlers and the loss of their natural habitat.

Did moa have wings?

No, moa are unique among ratites because they had no wing bones at all, making them completely flightless.

Which moa species was the largest?

The giant moa (Dinornis), specifically the females of the species, were the largest, reaching heights significantly greater than a human.

What did moa eat?

Moa were herbivores that browsed on various plants and vegetation found across the New Zealand islands.

Is it possible to bring moa back to life?

While there have been discussions and plans regarding de-extinction using ancient DNA, these remain theoretical and experimental goals.