The Bird Kingdom

How New Zealand became an evolutionary laboratory and a tragic example of island extinction.

BY Stefano Daza Arango

When the first Polynesians arrived on the shores of New Zealand between 1200 and 1300 AD [1], what they found was nothing less than a tropical island oasis. From its verdant forests to its lofty peaks, cascading fjords to its ivory shores, the island chain was stunning and bountiful. And for millions of years, it was a lost world ruled by birds [2]. 

Before the arrival of humans, New Zealand existed in a unique balance, teeming with a vast array of bird species, including owls, parrots, penguins, and song birds. And although birds were plentiful, the archipelago was almost completely devoid of land mammals [3]. This was because the landmass which was to become New Zealand split off from the supercontinent of Gondwana 80-85 million years ago, well before mammals and marsupials had a chance to evolve there [4]. The country’s only native terrestrial mammals are all bats [5], which flew in only later on the evolutionary timeline. 

Free from the threat of mammalian predators, New Zealand’s birds diversified into more than 200 spectacular species, with over 80% being endemic (only found there) and many being completely flightless. Flightlessness, a common trait in New Zealand, was a result of birds exploiting ecological niches that are usually occupied by ground-dwelling mammals. With no competition, many aves on the islands gave up their ability to fly and adapted to a life on the ground [4]. 

Last of the moas. Humans killed off the giant birds by overhunting.

(Moas were an easy source of food for the first humans of New Zealand. Overhunting quickly led to their extinction. Image:[6]).

The birds of prehistoric New Zealand must have been a sight to behold for the ancestors of the Māori people who first discovered this untouched land 700 years ago [1], but few must have shocked them as much as the giant moa (Dinornithiformes). For millions of years, nine varieties of these large flightless, wingless birds towered over the land. Reaching 12 feet in height and weighing in at over 550 lbs, the giant moa was a true avian colossal [6]. In comparison, ostriches today reach 9 feet tall and max out at 250 lbs [7]. The moas were New Zealand’s version of elephants, the dominant herbivores, and they played a special role in the ecosystem. It is estimated that between 500,000 and 2.5 million were present around the time of Polynesian settlement [4].

Prior to humans, giant moas had no natural predators to fear except for one: a gargantuan eagle that terrorized them from the skies. The Haast’s eagle (Harpagornis moorei) weighed an estimated 40 lbs and had a wingspan of over 10 feet long. It is the biggest eagle to have ever lived [9]. These massive birds of prey swooped down and pummeled their giant moa victims from behind, and scientists believe it is possible that they even prayed on early human settlers [10].

Early human settlers would have witnessed massive Haast’s predating on giant moas

(Early human settlers would have witnessed massive Haast’s predating on giant moas. Image:[11])

Peril in Paradise

The arrival of humans to New Zealand marked the beginning of the end for many of the country’s prehistoric avifauna and it kickstarted one of the fastest and largest extinction waves ever documented in recorded history. In just a few hundred years, this once-isolated, flourishing bird kingdom would suffer the tragic loss of more than half of all its avian species [12].

The first wave of extinctions began when Polynesians arrived and brought with them the kiore (Pacific rat) and the kurī (dog). Flightless and ground-nesting birds who had evolved for millions of years in the absence of mammalian predators had no defenses against these new threats, and were consequently no match for the invasive predators who preyed on them and their eggs. The humans, too, took advantage of the easy pickings on their newly discovered land. It is believed that first settlers could simply walk up to the giant moas, who had never encountered terrestrial mammals before and had no fear of man, and club them to death [5]. The fate of many a moa was sealed with a single swing. Just 100 years after the arrival of the Polynesians, giant moas and the fearsome Haast’s eagles that depended on them, were extinct [6].

In the 19th century Europeans arrived and brought with them a slew of new invasives, including more rats, rabbits, ferrets, weasels, stoats, possums, cats, pigs, goats, and dogs [5]. Some of these intruders were brought inadvertently, but many were released in an effort by the Europeans to create a “Mini-Europe” in the new land [4]. 

By predating on the native fauna that remained, the European-brought invasive species that arrived a mere 250 years ago further extinguished bird biodiversity while drastically changing the ecology of the country. Today, an estimated 25 million native birds are killed each year by invasive predators [13], and of those who managed to survive the initial onslaught, more than 30% are now at risk of extinction. Without immediate action, nearly two-thirds of New Zealand native birds could be under threat in the future [12].

Hope for Conservation and Restoration

In the midst of extinction, some native species found solace on offshore islands. Visionary early conservationists like Richard Henry saw the potential of these islands and chose to relocate threatened bird populations from the mainland to them, forming ‘arks’ of conservation [4]. In the 21st century, these offshore islands have become a beacon of hope, where introduced predators have been eliminated and the birdlife is bouncing back [5]. The ongoing recovery of iconic species like the flightless kākāpō, which resembles a large moss-colored owl and is the heaviest parrot alive today, serve as examples of the success behind the island conservation model.

The critically endangered kākāpō parrot

(The critically endangered kākāpō parrot. Image [13])

Nevertheless, kiwis aspire to restore their native avifauna to all of the country, not just small island sanctuaries. In a groundbreaking effort, the Department of Conservation set forth an ambitious plan to rid the country of its mammalian introduced predators by 2050 with its “Predator Free 2050” campaign [14]. The project is utilizing traditional techniques like trapping, monitoring, and poison baiting to accomplish the ambitious goal. Other methods, like traditional Māori pest controls and the use of biotechnology, are also being researched and considered [4]. After six years of work, the campaign has seen some remarkable accomplishments. The Department of Conservation has successfully protected a thousand square miles of land with predator control, eliminated predators from 117 of its islands, and created multiple predator-free reserves across the country [15].

A Cautionary Tale

Today, New Zealand’s national identity is tightly bound to its natural heritage. New Zealanders, for example, refer to themselves as “kiwis”; the small flightless bird with hair-like feathers and a long beak [4]. And although they’ve been extinct for centuries, Māori people still remember and revere the giant moas that greeted their ancestors on the shores 700 years ago.

As is the case with so many other island ecosystems, the fauna and flora that made prehistoric New Zealand so special was almost extinguished when the island entered the Anthropocene. It provides a cautionary story that underscores the single biggest threat that jeopardizes native biodiversity on islands around the globe today: invasive species 

Today, islands are on the front lines of the biodiversity crisis [12]. 75% of reptile bird, mammal and amphibian extinctions combined have occurred on islands [16]. Conservationists in Mauritius, the Galápagos, Hawai’i, and countless other islands are working to protect native wildlife often found nowhere else. 

Luckily, bold initiatives and innovative technologies are helping address the issue of biodiversity loss while helping restore and rewild island ecology. By both looking to the past and developing cutting edge tools, we have an opportunity to preserve the biological hotspots that are islands.

Like the dodos of Mauritius, the giant moas of New Zealand have become a symbol of extinction. But their stories are also fueling the next generation of scientists and conservationists to protect the natural beauty that remains, and restore the wonderful bird kingdom that was almost lost.


  1. “A Brief History.” Live & Work New Zealand.
  2. “The Wild, Wonderful & Weird Birds of New Zealand.” The Wild, Wonderful & Weird Birds of New Zealand, 1 Dec. 2022.
  3. Upholt, Boyce. “How a Giant Eagle Came to Dominate Ancient New Zealand.” Discover Magazine, Discover Magazine, 4 Sept. 2022.
  4. Kerr, Millie. “Chapter 3: The Land of Birds.” Wilder: How Rewilding Is Transforming Conservation and Changing the World, Bloomsbury Sigma, London, 2022.
  5. New Zealand Ministry for Culture and Heritage Te Manatu Taonga. “Fauna.” Te Ara Encyclopedia of New Zealand – Te Ara Encyclopedia of New Zealand, Ministry for Culture and Heritage Te Manatu Taonga, 20 July 2022.
  6. Morell, Virginia. “Why Did New Zealand’s Moas Go Extinct?” Science, 17 Mar. 2014.
  7. “Ostrich Fact Sheet.” PBS, Public Broadcasting Service, 27 Sept. 2021.
  8. Roy, Eleanor Ainge. “New Zealand Unveils Plans to Tackle Trade in Bones of Extinct Moa Birds.” The Guardian, Guardian News and Media, 2 July 2020.
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  10. Casey, Michael. “Extinct New Zealand Eagle May Have Eaten Humans.”,, 11 Sept. 2009.
  11. Holdaway, Richard, et al. “Lost in Time.” New Zealand Geographic.
  12. GrrlScientist. “It Would Take 50 Million Years to Recover New Zealand’s Lost Bird Species.” Forbes, Forbes Magazine, 13 Mar. 2020.
  13. “Kakapo.” EBird.
  14. “Predator Free 2050.” Pests and Threats.
  15. Mckenzie, Pete, and Jim Huylebroek. “New Zealand’s Biodiversity Crisis Prompts Extreme Measures.” The New York Times, The New York Times, 5 June 2022. 
  16. “The Importance of Islands.” Island Conservation, 7 Oct. 2021.
  17. Spencer, Christian. “Extinct Giant Bird Claw with the Flesh Still on It Resurfaces Online.” The Hill, The Hill, 27 May 2021.