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Moa

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The moa were a unique group of extinct, flightless birds. They belonged to the order Dinornithiformes and were once found only in New Zealand.

Moa size comparison
Moa size comparison

These birds were the dominant herbivores in New Zealand's forests, shrublands, and subalpine ecosystems. They filled the role of large land animals in these environments. Unlike other flightless birds, known as ratites, the moa were completely wingless. They lacked even vestigial wing bones, which are tiny leftover traces of wings found in other ratites. This made them truly distinct from their relatives.

Moa species varied greatly in their physical structure and size. During the Late Pleistocene-Holocene, there were nine species organized into six different genera. The two largest species were Dinornis robustus and Dinornis novaezelandiae. These giants could reach impressive heights with their necks fully outstretched. In contrast, the smallest species, the bush moa (Anomalopteryx didiformis), was roughly the size of a turkey.

Giant moa
Giant moa

Scientists have studied their skeletons to understand how they moved. While old reconstructions showed them standing very upright, new analysis of their vertebrae suggests they held their heads forward. This posture is similar to how a kiwi holds its head. This position allowed them to graze on low vegetation while still being able to browse trees.

Physical adaptations also helped moa survive in specific environments. Some species had specialized features for communication or weather. For example, two genera, Euryapteryx and Emeus, showed tracheal elongation. This means their trachea, or windpipe, formed a large loop inside their body cavity.

The skeletons of Eastern moa and other kinds of moas in Otago museum
The skeletons of Eastern moa and other kinds of moas in Otago museum

This feature is often associated with deep, resonant vocalizations that can travel long distances. Additionally, the Megalapteryx didinus had feathers that grew all the way down to its feet. This was likely an adaptation for living in high-altitude, snowy habitats. Their feathers could be reddish-brown, white, yellowish, or purplish, sometimes appearing speckled.

Our understanding of moa comes from remarkable biological finds. In the semiarid Central Otago region, the dry air helped preserve soft tissues through desiccation. This process created a form of natural mummy.

Megalapteryx feathers
Megalapteryx feathers

Many specimens have been recovered, including dried muscle on bones and even complete feathered legs. In 1864, gold miners found muscle on a Dinornis robustus bone at Tiger Hill. In 1870, skin and feathers were collected from Earnscleugh Cave. These preserved remains, such as the feathered leg from the Old Man Range in 1894, provide vital clues about their appearance.

Moa taxonomy, or the way scientists classify them, has been complex. Researchers once thought moa were closely related to the kiwi or the emu. However, genetic studies have revealed that their closest relatives are actually the flighted tinamous of South America.

Cuvier-67 Nandou d'Amérique
Cuvier-67 Nandou d'Amérique

Much of the confusion in classifying moa came from differences in size. Some differences were due to sexual dimorphism, where males and females look different. In the genus Dinornis, females were up to 150% as tall and 280% as heavy as males. These differences were so large that scientists originally classified them as separate species.

Other size variations were caused by environmental and temporal factors. For instance, specimens were often larger during the Otiran glacial period, which was the last ice age. There was also a north-south cline, meaning size changed based on location.

The skeleton of female upland moa
The skeleton of female upland moa

The history of the moa is also tied to the geography of New Zealand. During the Oligocene Drowning Maximum about 22 million years ago, much of the land was underwater. Only about 18% of present-day New Zealand remained above sea level. It is believed that moa ancestors survived on the South Island during this time and later recolonized the North Island.

The extinction of the moa happened very quickly after human arrival. When Polynesians settled New Zealand around 1300 C.E., the moa population was estimated to be between 58,000 and 2.5 million.

Moa mock hunt
Moa mock hunt

However, the birds became extinct within only 100 years of human settlement. This was primarily due to overhunting by humans. Before people arrived, the only predator of the moa was the massive Haast's eagle. The loss of the moa changed the entire ecosystem of New Zealand forever.

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🖼️ Images & Media (19)
File:Moa size comparison.png
Moa size comparison.png
File:Megalapteryx feathers.jpg
Megalapteryx feathers.jpg
File:The skeletons of Eastern moa and other kinds of moas in Otago museum.jpg
The skeletons of Eastern moa and other...
File:A book of birds (Plate I) (Struthio camelus).jpg
A book of birds (Plate I) (Struthio camelus).jpg
File:Cuvier-67 Nandou d'Amérique.jpg
Cuvier-67 Nandou d'Amérique.jpg
File:NothuraDarwiniiSmit white background.jpg
NothuraDarwiniiSmit white background.jpg
File:Euryapteryx.jpg
Euryapteryx.jpg
File:The genera of birds (white background).jpg
The genera of birds (white background).jpg
File:Mullerornis modestus (remaster).png
Mullerornis modestus (remaster).png
File:A monograph of the genus Casuarius (Casuarius unappendiculatus).jpg
A monograph of the genus Casuarius...
File:Dromaius novaehollandiae (white background).jpg
Dromaius novaehollandiae (white background).jpg
File:Giant moa.jpg
Giant moa.jpg

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