By John Kerr 10/08/2016

The New Zealand falcon, or kārearea, population is actually made up of two different subspecies, scientists have decided.

Researchers from Massey University declare the subspecies split in a new study analysing the physical and genetic differences between kārearea from different parts of the New Zealand. The research is published in IBIS, International Journal of Avian Science.

In collecting data on bird sizes, the researchers left no stone unturned. They dug up kārearea weights and measurements from studies dating back to the 1970’s as well data from frozen specimens of kārearea killed by accidental vehicle collisions, electrocution or poisoning and submitted to Department of Conservation offices. Preserved skins in the collections of Te Papa Museum of New Zealand, Canterbury Museum and Auckland War Memorial Museum were also examined.

two groups (squares and circles) identified by clustering of female kk wing and tail lengths
Two groups (squares and circles) identified by clustering of female kārearea wing and tail lengths. Trewick and Olley (2016).

Carefully analysing the size, weight and genetic differences of a total of 245 birds, the researchers found that kārearea fell into two distinct clusters – predominantly separating North Island and South Island individuals.

Study author, Professor Trewick of the Institute of Agriculture and Environment says, “kārearea vary considerably in size and colouration, over and above the differences between the males and females that are typical of raptors, and this variability has caused confusion since its earliest observation in the 1870s.

“Differences in size and other attributes among spatially separated populations could represent adaptation to local conditions and by recognising two distinct subspecies in kārearea, we will be able to identify the patterns of diversity within the species and understand the distinct evolutionary ecology of each.”

The supspecies have been named Falco novaeseelandiae novaeseelandiae from the South Island and Falco novaeseelandiae ferox for the smaller North Island form.

Size does matter. Above – northern kārearea female ‘Falco novaeseelandiae ferox’. Below – southern kārearea female ‘Falco novaeseelandiae novaeseelandiae‘. Credit Steven Trewick/Lena Olley.


The research was more than just an exercise in naming; identifying of subspecies allows conservationists to ensure that the distinct lineages preserved.

“This finding supports an informal conservation management strategy to avoid translocation and crossbreeding in captivity of falcons from the two islands,” says Professor Trewick.

The Department of Conservation estimates there are between 5,000 and 8,000 kārearea left, but this number is uncertain.

Read more about the research on


A bird in the hand is worth two in the bush. The kārearea features on the reverse of the New Zealand $20 note.
A bird in the hand is worth two in the bush. The kārearea features on the reverse of the New Zealand $20 note.

Featured image: Adapted from Wikimedia / Tony Mills. 

0 Responses to “NZ native falcon is actually two types of bird”

  • Read more about this research, the author writes…..
    Well, actually I’d like to read the original paper…. but it is paywalled.
    Obviously, a poor old NZ tax-paying pleb like me doesn’t need to read the work that my taxes support.

    Anyone higher up the food chain like to inform me if there is any genetic interchange between southern and northern forms?
    and how do the authors treat the older view that there are 3 forms of the NZ falcon?
    Ta muchly

  • Hi Maggy, don’t get me started on the issue of accessing peer reviewed research. I’m a huge proponent of open access and share your frustrations over the status quo of paywalled journals profiting from publicly funded research.

    In response to your questions: in my reading of the paper, I think the authors assume a degree of ‘recent or current’ gene flow between the islands: noting the wide range of falcons, they write:

    “In Karearea, the distribution of neutral genetic variation and pattern of size variation together indicate natural selection operating despite current or recent gene flow. Selection on functional loci that result in shifts of metabolic and predatory traits could proceed despite leakage at neutral loci. Such a process would be enhanced by any degree of gene flow limitation associated with a landscape feature such as the Cook Strait that influences intergenerational dispersal. Intraspecific competition that limits success of dispersing individuals and the habitat discontinuity associated with the Cook Strait seaway that marks a shift in environment could reduce gene flow.”

    Regarding the earlier divisions assigned to the NZ falcon, the authors state in their discussion: “A hierarchical analysis of molecular variance of population structure revealed no significant subdivision between samples assigned to three race classes (Bush, Eastern and Southern) on the basis of proposed range boundaries (Fox 1977). Pairwise comparison of population FST values did, however, show a significant though small departure from zero between the North Island and far south of the South Island.”

    I know that’s not as helpful as the full paper, but I hope it goes some way to answering your questions.

  • Don’t get me started on “open access”! It is NOT what it seems. Nothing is free. The public would quite likely end up paying significantly more under open access than under subscription access. It all depends on the details. If there are a large proportion of low interest papers open access, then the public pays in advance to free up stuff that almost nobody wants to read, and you can bet that publishers will set open access fees at an “optimistic” estimate of likely readership! Open access fees just divert research funding to publisher profits, and the publishers no longer worry if anyone bothers to read the stuff!

  • @ John Kerr,
    Thanks for your timely and informative reply.

  • Quite a few unfortunate seekers of paywalled scientific publications use Sci-Hub. Alleged criminals just have to enter the article’s DOI or PMID, and it will appear, and can even be downloaded as a pdf. Because it’s so convenient, some people with legal access also use Sci-Hub.

  • Sci-Hub is an interesting case. Any paywalled online science publication is just a free copy-paste away. The “criminals” are surely those who put the site up? Whether or not a small time “user” of the site is also a “criminal” is harder to determine. Maybe fair use/noncommercial use would be a defence? I don’t recommend taking the risk though. At any rate, as long as the site stays up, it is another good reason not to bother with open access, or else public money is wasted buying advance access to stuff that is already freely (if not entirely legally) available on Sci-Hub!