Circus eylesi
a.k.a the Eyles' Harrier
Name: Circus
eylesi.
Phonetic: Cir-cus ay-les-e.
Named By: Ron Scarlett - 1953.
Classification: Chordata, Aves,
Falconiformes/Accipitriformes?, Accipitridae (classification
depends upon the author as opinions differ between individuals).
Species: C. eylesi (type).
Diet: Carnivore.
Size: Wingspan up to about 2 meters long, with
females estimated about 2.5-3 kilograms in weight.
Known locations: New Zealand.
Time period: Pleistocene to Holocene. Exact date
of extinction is uncertain, but believed to be extinct at some point
between 1000AD and 1900AD. See main text for more detail.
Fossil representation: Several individuals though
usually by partial remains.
Named
in honour of the palaeontologist Jim Eyles, the Eyles' Harrier is
an extinct harrier, and one that grew to a particularly large size
for the kind of bird of prey that it was. The Eyles' Harrier is
often considered to have been similar to the modern day Swamp Harrier
(Circus approximans), though the Eyles'
Harrier is estimated to
have been two and half to three times heavier than a large Swamp
Harrier with a wingspan a quarter to two thirds as large as a Swamp
Harrier.
The
remains of Eyles' Harriers and Swamp Harriers can be both found in
New Zealand and from the same times, though an interesting thing of
note is that the Swamp Harrier does not seem to have become established
and widespread in New Zealand until after the Eyles' Harrier
disappeared. The Swamp Harrier is also known from nearby
locations such as Australia, Fiji, Vanuatu and New Caledonia, so
it’s possible that the earliest Swamp Harrier remains on New Zealand
may have been from visiting individuals that were either migrating or
simply searching out new hunting grounds. The fact the Swamp Harrier
did not begin to become established in New Zealand until the beginning
of the decline of the Eyles' Harrier suggests that the two birds were
so similar in ecological niche that the ecosystems of New Zealand could
not support both. The Eyles' Harriers being larger than the Swamp
Harriers, meant that they could drive off their smaller rivals.
Harriers
are noted for flying high above open ground and looking for ground
dwelling prey such as reptiles, small mammals and birds that lived on
the ground. As such is probable that Eyles' Harriers hunted in a
similar fashion, except they hunted the smaller ground dwelling
animals of Pleistocene/Holocene New Zealand. It is likely that during
this time the Eyles' Harriers were among the apex predators of New
Zealand, though the largest bird of prey here that lived at the same
time as the Eyles' Harriers was the Haast’s
Eagle, the inspiration
for the pouakai bird of Maori legend and a much heavier bird of prey
that specialised in hunting the moa
birds of New Zealand.
Both
the Eyles' Harrier and the Haast’s Eagle were among the largest birds
of prey for their respective types, and both seem to have suffered
and gone extinct from the same cause; human habitation. The first
people are believed to have settled New Zealand around 1250-1300AD,
and the establishment of permanent settlements led to two things;
the clearing of habitats and the hunting of the larger animals on the
islands for food. By about 1400AD, the moa were gone, and the
Haast’s Eagle disappeared along with them. No one knows for certain
when the Eyles' Harriers went extinct, but since they were
generalists, they had the chance to survive for a bit longer, but
continued pressure from people and perhaps even Swamp Harriers could
have driven them into extinction. With people hunting the larger
game, only smaller animals that were harder to catch and offered less
food were available to the Eyles' Harriers. The Swamp Harriers
however were smaller, more nimble and did not need to eat as much
food to survive, and could have steadily replaced Eyles' Harriers
as they steadily declined in numbers from lack of suitable prey.
This
is analogous to what happened in North America between Dire
Wolves
(Canis dirus) and Grey Wolves (Canis
lupus) at the end of the
Pleistocene. A marked decline in large animals occurred at this
time, which may or may not be in part due to the appearance of the
first people on this continent, but the point here is that the
decline of larger prey had a knock on effect which caused the decline
of the large predators. Similar but smaller predators however,
managed to survive into modern times simply because they did not need
to eat as much to survive, which is why there are Grey Wolves in
North America today, but no longer any Dire Wolves.
It
is just possible that Eyles' Harriers may have managed to survive
until the late nineteenth century. This idea is centred around the
claim that when travelling the Landsborough River Valley in the
1870s, explorer Charles Edward Douglas shot and subsequently ate two
raptors of notably large size. Douglas claimed these to have been two
pouakai, a legendary bird of Maori legend believed to have had its
origin from early encounters between early settlers and Haast’s
Eagles. But Maori people of the time insisted that the pouakai was a
bird not seen in living memory, and the disappearance of the moa
several hundred years earlier also supports this. Instead it is more
probable that the birds in question may have actually been Eyles'
Harriers since their extinction seems to have been slower and not so
directly tied with one event.
The
Eyles' Harrier can be taken as an example of insular gigantism,
however, at the other end of the scale there is another prehistoric
harrier that lived in the Pacific which serves as an example of insular
dwarfism. This is the Wood
Harrier.
Further reading
- New Zealand’s pre-human avifauna and its vulnerability -
Richard N. Holdaway - 1989.
- A reappraisal of the late Quaternary fossil vertebrates of Pyramid
Valley Swamp, North Canterbury, New Zealand - Richard N.
Holdaway & Trevor H. Worthy - 1997.
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