The Moa Birds of New Zealand
The early discoveries
Not
long after the first European settlers arrived in New Zealand,
stories about giant birds that once existed upon the Islands began to
filter out, reaching all over the world. The European settlers
initially only had Maori stories to go on, but in time the remains of
large flightless birds began to be found, and it was soon established
that before the arrival of humans upon New Zealand, the moa were the
largest terrestrial animals upon the islands of New Zealand. In the
early days of moa study, a lot of things were assumed about these
birds, but almost two centuries of scientific study later, and a
lot more detail about these birds is now known.
Taxonomics
The
word moa is actually the Māori word for describing these birds. This
word is also both singular and plural, which means that a single moa
standing in a field could be called a moa, whereas a whole bunch of
these birds standing in a field would also be just called moa. The
word usage is the same as if you were using the word sheep.
The
moa birds can be further divided into specific genera that in some
cases can be further divided into species. For the most part this
article will describe the moa birds as just moa, but in some
instances specific genera will be singled out. We’re also going to
avoid calling the genera and species by their more common names to try
and avoid confusion, but the common names are added to the genus
names in a list at the very end of the article.
Early
on, moa genera suffered from what is now termed the ‘wastebasket
taxon’ effect, which is where similar remains to those already
named would be simply labelled as an additional species without too
much further thought. However it must be understood that this took
place in the mid and latter half of the nineteenth century when the
science of palaeontology was still in its infancy and it was difficult
for researchers to stay up to date with new discoveries since global
communications still largely had to be hand delivered. This led to a
great many species of moa being named and established, but many of
these have now been dismissed as invalid.
Later
palaeontologists began noticing that many remains from different
locations actually were the same as those from other locations, and
thus were the same as the aforementioned species. Some also noticed
that some species were actually juveniles of already named adults,
and so the species lists shrank further. The biggest insight came
about however when male and female birds began to be more positively
identified. This led to the discovery that male moa birds tended to
be smaller than female moa, yet at the time the male moa were being
classed as different species by the first researchers of the nineteenth
century because of the size difference. This led to the final
reduction of species named so that today only a handful of the once
named species are considered to be valid, those which are not are now
synonyms to these valid species.
New
discoveries in the future may lead to the creation of new genera and
species, but the existing moa bird remains are still giving up their
secrets. This is because many moa remains are actually still testable
for DNA, and DNA analysis of some of these remains has revealed that
although they are physically similar in appearance, they are slightly
different to the DNA sampled from other remains, which indicates that
they are actually different species. Therefore the future of moa
taxonomy is what you might term semi-fluid; the established genera
and species are considered to be valid, but there may be further
species lurking within them waiting to be discovered.
The
moa have been assigned to the ratite family of birds which today are
noted for being cursorial (ground dwelling) in their nature. For
a long time moa were thought to have been related to other flightless
birds from New Zealand (Apteryx) such as the
kiwi, cassowary
(Casuarius), and even the Australian emu (Dromaius).
However
in 2010 a study by Philips et al revealed that the closest known
living relative of the moa birds are now actually living in South
America and are known as tinamous. This is surprising, not only
because of the geographic distance of South America from New Zealand,
but that the tinamou birds are not actually ratites, but form a
closely related sister group called the Tinamiformes.
What were the moa like?
In
the simplest terms the moa were heavily built birds that walked around
on two powerfully built legs. The leg proportions however do not
match those of fast running birds which suggests that moa were
relatively slow for their leg length. It should be remembered however
that there were no large ground predators known to have existed in New
Zealand until the arrival of the first people, so the ability to run
fast would have really been an unnecessary option anyway.
The
moa are a good example of the extreme effects of being secondarily
flightless. The moa were certainly descended from ancestors that were
capable of flight; it is the only way birds could have feasibly
reached the islands of New Zealand. Whereas many secondarily
flightless birds still retained smaller versions of their ancestors
wings however, the wings of the moa had completely disappeared.
Why some birds lose the ability to fly is always a matter of
contention, but for the moa it seems that an abundant supply of food
combined with no ground predators meant that there was simply no need
to expend energy upon flying to escape or search for food.
Aside
from losing their wings, the feathers on the body also devolved to
more simple hair-like structures. These would not have been capable
of creating lift for flight, but they would have still performed an
important insulatory function as well as allowing rain to run off the
body without getting the skin wet. Analysis of feather pigments has
also revealed that moa could be quite variable in their colour, with
the genus Dinornis
having feathers that were red/brown in their
colouration, to the genus Emeus
which had feathers that were more of
a beige colour.
Due
to their large physical size, especially genera such as Dinornis,
early reconstructions of moa were usually done with the deliberate
intention of making them appear as tall as possible. This meant
posing skeletons so that they were stood as erect as possible, with
even the neck connecting to the base of the skull. This was a mistake
however given that the neck vertebrae actually connect to the back of
the skull, indicating that the head was actually carried more forward
from the body rather than above it. This arrangement also allowed moa
a broad range of motion, cropping at plants near the ground to
reaching up to the lower branches of the tree canopy.
Moa
birds are noted for having downward curving beaks that are often termed
secateur like (secateurs are special pruning shears for snipping
plant branches). These beaks would allow moa to slice off choice
parts of plants before swallowing the mouthful which was then processed
further by gastroliths held within the gizzard. Stomach contents and
coprolites of moa birds have been analysed which reveal that moa would
feed upon a variety of different plants, eating parts such as leaves
and green twigs.
As
already briefly mentioned above, the female moa were larger than the
males. In some genera the size difference was fairly slight, but in
others the female could be anything between one and a half to twice as
large as the male.
Moa breeding
Remains
of eggs and juveniles all seem to indicate that the moa birds followed
a k-strategy method when it came to survival. What k-strategy means
is that when moa raised young they would only attempt to raise one to
two or three chicks at a time. By only raising a small number, the
parents could invest more time and attention in rearing the young,
thus increasing their chances of surviving to adulthood. Studies of
bone grow growth of moa have revealed that it would take up to ten
years for a moa bird to reach reproductive maturity.
The
opposite of k-strategy is r-strategy, and this is where large amounts
of young are born with the expectation that most will be killed by
predators while a few will survive to adulthood and reproduce
themselves. Here the sheer weight of numbers ensures the species
survival rather than parental ability. The main drawback of a
k-strategy method of reproduction is that population growth is always
much slower, and hence populations take much longer to recover after
sudden declines. This might also explain why moa birds eventually
went extinct after the ecosystems of New Zealand were upset by the
arrival of the first people.
Moa
seem to have preferred to nest amongst the shelter of rocks where
interpretations state that parent birds scratched out notches in
pumice (a form of solidified lava) with their toe claws. After
this they seem to have covered the nest with plant material to provide
a soft and warm lining for incubating their eggs. The size of the
eggs depends upon the genus/species involved, but even smaller
species eggs could be as much as twelve centimetres long, with eggs
of larger species being up to twenty-four centimetres long. Moa
eggshells however were very thin for their size, around one
millimetre thick, something which has led to reasonable speculation
that male moa may have sat on and incubated the eggs since their
smaller physical size meant that they were much lighter than the
females, and hence less likely to accidentally cause damage to the
eggshell.
The
collected remains of eggshells and moa in some locations has led to
reports of moa breeding in large colonies, however modern analysis
and thinking suggests that these collections are the results of small
amounts of remains steadily building up over a long period of time.
This is the same principal regarding the discovery of Pleistocene
mammals in places like Europe, and in this respect we’ll quickly
cover the now extinct cave bears (Ursus
spelaeus). Cave bears got
their name from their fossils being discovered in cave deposits, and
what excited the first discoverers of these remains is that fossils
belonging to several hundred individuals were found within the cave
sediments. This led to early depictions of cave bears living in
anything from a dozen to several hundred bears per cave at the same
time.
Modern
analysis of these remains however leads to a much more likely notion of
there only ever being one bear (not including any young) living in
a cave at any one time, but the cave being repeatedly inhabited by a
successive line of bears after the death of the previous occupant.
Rock formations can remain unchanged for hundreds of thousands to
millions of years, which means that a cave that provides a suitable
shelter, may still be being used by the same species of animal one
hundred thousand years later as long as it is largely unchanged.
For the sake of argument we’ll say that a cave bear could live for
about twenty years on average before dying from natural courses. Over
a course of one hundred thousand years divided by an average lifespan
of some twenty years, around five thousand individual bears could
call that cave home during that time period, and assuming that they
all died within that cave, their bones would all collect together
into one seemingly huge deposit. A few thousand years later and an
eager naturalist discovers this accumulation of bones and suggests that
some five thousand bears lived together in this cave, and you can
appreciate how this misconception got started.
Back
to New Zealand and the moa birds, and the same principal applies.
Suitable sheltered locations for rearing young would have been few and
far between, so good spots would have been repeatedly used over and
over the millennia by successive generations of moa. The accumulated
detritus of eggshell fragments and bones over these thousands of years
could just as easily result in the false interpretation of these being
breeding colonies as to what happened with the early interpretation of
cave bears of Europe.
Moa mummies
Some
of the most exciting finds relating to moa birds are the mummified
remains of some individuals. This are naturally preserved individuals
that lived and died at high elevations where the moisture content of
the air is far less than it is nearer sea level and in moist
environments such as forests. In addition, these locations are
usually more exposed to prevailing winds which can accelerate the
drying process further.
The
main genera known to have mummified remains are Euryapteryx
and
Megalapteryx
and between them these include soft tissues such as muscle
and tendons, of the head, neck, leg and even a complete foot.
These mummified remains have offered researchers a rare glimpse into
how exactly moa were put together beyond just their bones.
Predators of the moa
Prehistoric
New Zealand during the Pleistocene was a land dominated by birds.
Mammals seems to be absent from New Zealand, though new discoveries
coming to light as of 2013 seem to indicate that New Zealand may
have actually had a population of small mammals. The only
definitively known native mammal is a bat, and the only other
vertebrates were reptiles like the Tuatara. After this there are of
course invertebrates like insects, but none of these animals seem to
have been capable of posing a threat to moa.
To
find natural predators of the moa we have to look again to the birds,
and here there is one serious contender that is believed to have
hunted moa exclusively: the Haast’s
eagle. Big animals often have
big predators, and while the Haast’s eagle may not have had a
wingspan as large as some of today’s largest eagles, the Haast’s
eagle was almost certainly the heaviest eagle that we know about to
ever take to the air. Female Haast’s eagles have been estimated to
weigh in the range of ten to fifteen kilograms in weight, whereas the
largest recorded eagle living in captivity (and hence well fed)
only reached nine kilograms in weight.
The
relatively short wingspan of the Haast’s eagle was actually one of its
main advantages when it came to hunting moa. In order to track down
moa birds, Haast’s eagles would have been hunting and flying in
forested environments, and a shorter wingspan meant that Haast’s
eagles could fly amongst the trees without clipping their wings on them
as they approached their targets. Haast’s eagles are believed to have
struck moa birds at high speeds, driving their powerful six to ten
centimetre long talons into the spines of their prey, crippling them
almost instantly.
There
is also another bird that may have hunted moa, and this is the
Eyles’
harrier. Although no way near as large as the Haast’s
eagle, the Eyles harrier was still large enough to be a threat to
small juvenile moa that may have strayed too far from their parents.
Both the Haast’s eagle and the Eyles harrier are now extinct, though
they seem to have gone at different times. The Haast’s eagle
disappears at some point soon after 1400AD, the same time as the
moa largely disappeared. This indicates that the Haast’s eagle was a
specialist at hunting the moa, and when they disappeared, they were
unable to adapt to a new prey source. Eyles’ harriers however are
thought to have been generalists and while capable of hunting small
individual juveniles, they likely also hunted other types of birds.
However, as the environments of New Zealand and available prey birds
changed and declined, they too disappeared.
Extinction of the moa
Around
1250-1300AD the proverbial death knell was sounded for the moa when
the first humans reached New Zealand. The moa were apparently quite
docile in nature, something that came about from the lack of large
ground predators in New Zealand up until that point. Finding
themselves in a new land the first people there, the Māori,
needed food to eat, and the presence of large birds that could feed
many people and did not immediately run away would have been the
obvious choice. Human hunting was not the only factor to contribute
to the demise of the moa, habitat destruction would have also been a
further strain upon them. New populations of people need to clear
land to build settlements, and eventually clear more to grow plants
to eat.
There
were two further additions to the moa survival problem caused by the
arrival of the first people. First was the kuri,
also known as the
Polynesian dog, and apart from being used by hunters to assist in
hunting moa, feral populations of these dogs may have also formed
packs and hunted moa and other ground dwelling birds of their own
accord. Second, was the introduction of the Polynesian rat, a
more accidental arrival but one that could have fed upon unattended
eggs and newly hatched chicks incapable of running away.
As
already mentioned above, moa birds followed a k-strategy survival
method. With large numbers of moa being killed off for food, the
population simply could not grow fast enough to replenish the numbers
lost from hunting. A further factor is that as the numbers declined
fewer opportunities were there for individuals to pair up, meaning
that incidents of breeding actually happening began to decline as
well. With the pressure on the moa unrelenting, their populations
quickly reached a point where they could not recover in the face of a
changed ecosystem.
The
most recent confirmed moa fossils are dated to around the year
1400AD, and it was also at about this time that the fossils of the
main indigenous predator of the moa, the Haast’s Eagle disappeared.
Aside from further underlining the intimate predator/prey relationship
between these birds, this also indicates that by this time moa where
very scarce. Not everyone is convinced however that the moa died out
at this time or indeed that they are extinct at all.
Survivors? (sightings and
cloning)
As
far as hard science is concerned, the moa perished around the year
1400AD, possibly lasting up to a few decades after. This date is
easy to accept because there is a lot of evidence to support it,
namely, a lot of moa remains go up to this point and then rather
suddenly drop off. However, it is possible that some moa existed
past this mark, the question is, how far?
There
have been isolated reports of people encountering moa in some of the
remotest regions of New Zealand all the way up until the end of the
nineteenth century. These have come from Maori hunters stalking
animals through the countryside, sailors sighting moa on coastlines
to farmers spotting a moa as they managed their land. Even footprints
have occasionally been reported. Unfortunately, there is no hard
evidence such as photographs to confirm any of these sightings,
although granted, back in those days camera equipment was very new
and only owned by a small number of people. By contrast today,
almost every single person possesses the capacity to document
sightings, even if only with a mobile phone camera.
There
have however been claims of footprints to even photographs of objects
that are claimed to be living moa that have managed to survive into
modern times. Unfortunately these photographs, just like those
claiming to depict mammoths in the Russian Federation, or Bigfoot in
North America are almost always so blurry and at such extreme distances
that nothing can be clearly defined and identified.
You
have to appreciate that often hoaxes get made just to see how many
people can be fooled, and now that image editing software like
Photoshop is more available to everyday people instead of just
professionals, it is easier than ever to create images. Assuming
that no malicious intent is intended, misidentification is also
another factor. A small bird with moa-like proportions gets
photographed in such a way that it appears to be a much larger bird
seen from further away.
An
analogy to the above would be reports of big cats roaming the British
Isles. Although authorities concede that it is probable that some big
cats like leopards were released into the British countryside after the
introduction of the Dangerous Wild Animals Act in 1976 which
required keepers of these animals to have a special license, many
photographs of animals supposedly depicting predators like leopards and
panthers have later been revealed to be nothing more than domestic
house cats shot against backdrops that at range coincidentally make
them appear to be bigger than they actually are.
Perhaps
a more exciting prospect for the future would be the possibility of
genetic cloning. The relatively high state of preservation of some
moa remains have allowed for genome mapping to take place, and with
continuing advances in genetic engineering, most scientists concede
that it will only be a matter of time before an attempt is made to
resurrect a long extinct animal, and with the available remains
known, the moa birds may one day be possible candidates for this.
Anomalopteryx
- a.k.a. Lesser Moa, Little Bush Moa, Bush Moa.
Dinornis
- North Island Giant Moa (D. novaezealandiae), South Island
Giant Moa (D. robustus).
Emeus
- Eastern Moa.
Euryapteryx
- a.k.a. Coastal Moa, Broad Billed moa and Stout Legged Moa.
Megalapteryx
- Upland Moa.
Pachyornis
- Heavy-footed Moa (P. elephantopus), Mantell’s Moa (P.
geranoides), and Crested Moa (P. australis).
Further reading
- On the remains of Dinornis, an extinct
gigantic struthious bird
- Richard Owen - 1843.
- Description of Dinornis crassus -
Proceedings of the Zoological
Society of London 1846: 46 - Richard Owen - 1846.
- Avium systema naturale - Expedition der vollständigsten
Naturgeschichte - Ludwig Reichenbach - 1852.
- Genus Pachyornis - Catalogue of the Fossil
Birds in the British
Museum (Natural History) - Richard Lydekker - 1891.
- The diet of moas based on gizzard contents samples from Pyramid
Valley, North Canterbury, and Scaifes Lagoon, Lake Wanaka, Otago -
Records of the Canterbury Museum 9: 309–336. - Colin James Burrows,
Beverley McCulloch & Michael Malthus Trotter - 1981.
- And then there were twelve: the taxonomic status of Anomalopteryx
oweni (Aves: Dinornithidae) - Notornis 29 (1): 165–170 - P.
R. Millener
- 1982.
- A partially mummified skeleton of Anomalopteryx didiformis
from
Southland - Journal of the Royal Society of New Zealand 17: 399–408 -
R. M. Forrest - 1987.
- Mummified moa remains from Mt Owen, northwest Nelson -
Notornis 36 (1): 36–38. - Trevor H. Worthy - 1989.
- On evidence for the survival of moa in European Fiordland - New
Zealand Journal of Ecology 12 (Supplement): 39–44 - A. Anderson - 1989.
- Unique, dark olive-green moa eggshell from Redcliffe Hill,
Rakaia Gorge, Canterbury - Notornis 39 (1): 63–65.
- Beverley McCulloch - 1992.
- Quaternary fossil faunas from caves in the Punakaiki area, West
Coast, South Island, New Zealand - Journal of the Royal Society of New
Zealand 23: 147–254 - T. H. Worthy & R. N. Holdaway - 1993.
- Quaternary fossil faunas from caves in Takaka Valley and on Takaka
Hill, northwest Nelson, South Island, New Zealand - Journal of the
Royal Society of New Zealand 24 (3): 297–391 - T. H. Worthy &
R. N. Holdaway - 1994.
- Quaternary fossil faunas from caves on Mt. Cookson, North Canterbury,
South Island, New Zealand - Journal of the Royal Society of New Zealand
25 (3): 333–370 - T. H. Worthy & R. N. Holdaway - 1995.
- Morphology, myology, collagen and DNA of a mummified moa,
Megalapteryx didinus (Aves: Dinornithiformes) from
New Zealand -
Tuhinga: Records of the Museum of New Zealand Te Papa Tongarewa 4: 1–26
- P. Vickers-Rich, P. Trusler, M. J. Rowley, A. Cooper, G. K. Chambers,
W. J. Bock, P. R. Millener, T. H. Worthy & J. C. Yaldwyn - 1995.
- A reappraisal of the late Quaternary fossil vertebrates of Pyramid
Valley Swamp, North Canterbury - New Zealand Journal of Zoology 24:
69–121 - R. N. Holdaway & T. H. Worthy - 1997.
- Quaternary fossil faunas of Otago, South Island, New Zealand -
Journal of the Royal Society of New Zealand 28 (3): 421–521 - Trevor
H. Worthy - 1998a.
- The Quaternary fossil avifauna of Southland, South Island, New
Zealand - Journal of the Royal Society of New Zealand 28 (4): 537–589 -
Trevor H. Worthy - 1998b.
- A preliminary report on the nesting habits of moas in the East Coast
of the North Island - Notornis 46: 457–460 - W. H. hartree - 1999.
- Rapid Extinction of the Moas (Aves: Dinornithiformes): Model, Test,
and Implications - Science 287 (5461): 2250–2254 - R. N. Holdaway
& C. Jacomb - 2000.
- Extreme reversed sexual size dimorphism in the extinct New Zealand
moa Dinornis - Michael Bruce, Trevor H.
Worthy, Tom Ford,
Will Hoppitt, Eske Willerslev, Alexei Drummond & Alan
Cooper - 2003.
- Nuclear DNA sequences detect species limits in ancient moa -
L. Huynen, C. D. Millar, R. P. Scofield & D.
M. Lambert - 2003.
- Plant remains in coprolites: diet of a subalpine moa
(Dinornithiformes) from southern New Zealand. - Emu Austral
Ornithology - Mark Horrocks, Donna D'Costa, Rod Wallace, Rhys
Gardner & Renzo Kondo - 2004.
- Reconstructing the tempo and mode of evolution in an extinct clade
of birds with ancient DNA: The giant moas of New Zealand -
Proceedings of the National Academy of Sciences 102 (23):
8257–8262 - Allan J. Baker, Leon J. Huynen, Oliver
Haddrath, Craig D. Millar & David M. Lambert - 2005.
- Cortical growth marks reveal extended juvenile development in New
Zealand moa - Nature 435 (7044): 940–943 - Samuel T. Turvey, Owen R.
Green & Richard N. Holdaway - 2005.
- Rediscovery of the types of Dinornis curtus
Owen and Palapteryx
geranoides Owen, with a new synonymy (Aves:
Dinornithiformes)
- Tuhinga (16): 33–43 - Trevor H. Worthy - 2005.
- Moa gizzard content analyses: further information on the diet of
Dinornis robustus and Emeus crassus, and the first evidence for the
diet of Pachyornis elephantopus (Aves:
Dinornithiformes) - Records of
the Canterbury Museum 21: 27–39 - J. R. Wood - 2007.
- Eggshell characteristics of moa eggs (Aves: Dinornithiformes) -
Journal of the Royal Society of New Zealand 37 (4): 139–150 - B. J.
Gill - 2007.
- A deposition mechanism for Holocene miring bone deposits, South
Island, New Zealand - Journal of Taphonomy 6: 1–20 - J. R. Wood, T. H.
Worthy, N. J. Rawlence, S. M. Jones & S. E. Read - 2008.
- Moa (Aves: Dinornithiformes) nesting material from rockshelters in
the semi-arid interior of South Island, New Zealand - Journal of the
Royal Society of New Zealand 38 (3): 115–129 - J. R. Wood - 2008.
- The evolutionary history of the extinct ratite moa and New Zealand
Neogene paleogeography - Proceedings of the National Academy of
Sciences 106 (49): 20646 - M. Bunce, T. H. Worthy,
M. J. Phillips, R. N. Holdaway, E. Willerslev, J.
Haile, B. Shapiro, R. P. Scofield, A. Drummond, P.
J. J. Kamp & A. Cooper - 2009.
- Ancient DNA Reveals Extreme Egg Morphology and Nesting Behavior in
New Zealand's Extinct Moa - Proceedings of the National Academy of
Sciences 107 (30): 16201 - Leon Huynen, Brian J. Gill, Craig D. Millar,
David M. Lambert - 2010.
- Tinamous and Moa Flock Together: Mitochondrial Genome Sequence
Analysis Reveals Independent Losses of Flight among Ratites -
Systematic Biology 59 (1): 90–107 - Matthew J. Phillips, Gillian C.
Gibb, Elizabeth A. Crimp & David Penny - 2010.
- Twenty-first century advances in knowledge of the biology of moa
(Aves: Dinornithiformes): A new morphological analysis and moa
diagnoses revised - New Zealand Journal of Zoology 39 (2):
87 - T. H. Worthy & R. P. Scofield - 2012.
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