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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