Northern Brown Kiwi (Apteryx mantelli): downlist to Vulnerable?

This discussion was first published as part of the 2016 Red List update. At the time a decision regarding its status was pended, but to enable potential reassessment of this species as part of the 2017 Red List update this post remains open and the date of posting has been updated.

Apteryx mantelli occurs in isolated and fragmented populations on the North Island and some adjacent islands of New Zealand. Birds are locally common in Northland, the northern and central Coromandel Peninsula, southern Bay of Plenty, and in a triangle between Tongariro, Whanganui and Waitara in north Taranaki. They are more sparsely distributed in southern Coromandel Peninsula, western Bay of Plenty, north Taranaki, and from Motu to the northern Ruahine Range. Stable populations are present on Little Barrier/Hauturu-o-Toi (c.1,000 birds), Kawau and Ponui Islands (Heather and Robertson 2015, H. A. Robertson in litt. 2016). Since 1991, they have been successfully introduced to three pest-free offshore islands (Motukawanui, Motuora, and Motutapu), and translocated to many mainland sites that are either pest-free or where pests are maintained at very low densities. These translocations have established new populations (e.g. Marunui, Mataia, Tawharanui, Maungatautari, Lake Rotokare, Cape Kidnappers, Pukaha Mount Bruce and Rimutaka Range) or have bolstered severely depleted populations (e.g. Whangarei Heads, Mt Egmont National Park, Boundary Stream) (Heather & Robertson 2015, H. Robertson in litt. 2016).

In 1996, the total population of A. mantelli  was estimated to number 35,000 individuals. In 2008, this was estimated at 25,000 (Holzapfel et al. 2008). In 2015, the estimated number of individuals in the four main populations was: 8,200 in Northland, 1000 on Little Barrier, 1,700 on the Coromandel Peninsula, 7,150 in the eastern North Island and 7,500 in the western North Island, giving a total of c.25,550 birds (H. Robertson in litt. 2016). This is consistent with the estimate in 2008, indicating that the population has remained stable for the last eight years.

Unmanaged mainland populations are still declining at 2.5% per annum owing to introduced predators (Robertson et al. 2011). However, this is now thought to be balanced by population increases in areas where predators are absent or managed to low densities (H. Robertson in litt. 2016). Since the overall population is no longer declining rapidly, this species no longer qualifies as Endangered under criteria A2bce+3bce+4bce under which it was previously listed. It is suggested therefore that A. mantelli be downlisted to Vulnerable under criterion A2bce as there has been a population reduction of more than 30% but less than 50% over three generations (26 years) and the causes of the reduction are understood but have not ceased and are not reversible. Introduced predators are still present in New Zealand, but it is clear that with good conservation management, kiwi populations can now be maintained and increased. More than 1,000 individuals of this species are also present on pest-free offshore islands, especially Hauturu-o-Toi/Little Barrier which gives the species some extra protection. It is clear that the continued stability of, and any future increase in A. mantelli population numbers will be dependent on the continuation of conservation action by government and community groups (Robertson in litt. 2016).

Additional information and comments on this proposal are welcomed.

 

References:

Heather, B. D.; Robertson, H. A. 2015. The field guide to the birds of New Zealand. Penguin Random House NZ, Auckland, New Zealand.

Holzapfel, S., Robertson, H. A., McLennan, J. A., Sporle, W., Hackwell, K. and Impey, M. (2008) Kiwi (Apteryx spp.) recovery plan: 2008–2018. Wellington, New Zealand: Department of Conservation.

Robertson, H.A., Colbourne, R.A., Graham, P.J., Miller, P.J. and Pierce, R.J. 2011. Experimental management of Brown Kiwi Apteryx mantelli in central Northland, New Zealand. Bird Conservation International 21: 207-220.

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5 Responses to Northern Brown Kiwi (Apteryx mantelli): downlist to Vulnerable?

  1. James Westrip (BirdLife) says:

    Based on available information, our proposal for the 2016 Red List would be to pend the decision on this species and keep this discussion open until 2017, while leaving the current Red List category unchanged in the 2016 update.

    Final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  2. Rod Hitchmough says:

    We’ve assessed generation time as 25 years, so the 3-generation assessment period as 75 years. That may be too generous, but kiwi live for many decades in the absence of invasive predators, and don’t begin breeding until 4-5 years (though they’ll breed younger when released into empty habitat first breeding would probably be even later in the absence of territorial vacancies created by invasive predators), so 3 generations in 26 years seems way too low.

    The assessment above seems otherwise accurate but the plateauing of the decline is very recent when compared to the overall assessment period, and in most places is totally dependent on the on-going input of highly enthused community groups. The ability of those groups to survive generational turnover has not yet been tested.

  3. James Westrip (BirdLife) says:

    The New Zealand national status of this species has recently been re-assessed in the Conservation Status of New Zealand birds, 2016 (Robertson et al. 2017). There are differences in the Categories, Criteria and Thresholds for listing between Robertson et al. (2017) and those used when conducting IUCN Red List assessments, but in Robertson et al. (2017) Northern Brown Kiwi was listed as Nationally At Risk as a Declining taxon under criterion B(1/1). This means the species was assessed to have a population of 20,000-100,000 mature individuals with a predicted decline of 10-50%.

    Reference
    Robertson, H. A.; Baird, K.; Dowding, J. E.; Elliott, G. P.; Hitchmough, R. A.; Miskelly, C. M.; McArthur, N.; O’Donnell, C. F. J.; Sagar, P. M.; Scofield, R. P.; Taylor, G. A. 2017. Conservation status of New Zealand birds, 2016. New Zealand Threat Classification Series 19. Department of Conservation, Wellington. http://www.doc.govt.nz/Documents/science-and-technical/nztcs19entire.pdf

  4. Hugh Robertson says:

    The causes of population declines are understood (especially introduced mammalian predators), are continuing, but are reversible. Over the past 5-10 years, declines have been reversed in many parts of the range of the species and the total species population has stabilised or is now slowly increasing. Recent new government funding has further boosted management of the species, especially by supporting community group efforts, and increasing the use of ONE and creches in predator-free sanctuaries. The NZ assessment in 2016 that they are At Risk – Declining was precautionary and a case could be made for “At Risk – Recovering” to have been used, but the period of recovery is relatively short compared with the 75 year period for 3 generations noted by Rod Hitchmough above. The 26 years noted in the original was an estimate for a single generation length (not for 3 generations). I support downlisting to Vulnerable.

  5. Hannah Wheatley (BirdLife) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2017 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.

    There is now a period for further comments until the final deadline of 4 August, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from those in the initial proposal.

    The final 2017 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN

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