Experimental management of Brown Kiwi Apteryx mantelli in central Northland, New Zealand

Abstract

SummaryThe population growth of Brown Kiwi Apteryx mantelli was measured under four different management regimes: unmanaged, predator trapping, predator poisoning, and Bank of New Zealand Operation Nest Eggä (BNZONE) -the removal of eggs for artificial incubation and return of resultant subadults to the wild. Life table analysis revealed that high adult mortality (7.3% per annum), caused mainly by domestic dog Canis familiaris and Ferret Mustela furo predation was the critical factor affecting Brown Kiwi populations in central Northland. The 13.8-year life expectancy of adults was only one-third of what can be expected in the absence of these two predators. Predation of Brown Kiwi chicks and juveniles (, 1 kg) by Stoats Mustela erminea and, to a lesser extent, domestic cats Felis catus, was also important. Unmanaged populations declined at 2.5% per annum. Trapping pests in a 200 ha area was largely ineffective, with the population declining by 1.7% per annum. Poisoning pests allowed Brown Kiwi populations to increase at 3.3% per annum. BNZONE proved to be by far the most effective tool, resulting in a 12.5% annual population increase, mainly due to 83% chick survival to six months old, compared with 10% survival in unmanaged sites. There were no observable behavioural problems associated with chicks being reared ex situ, but BNZONE was the most expensive tool and benefited only the Brown Kiwi. This study has helped to develop a range of tools that are now being used to facilitate recovery of populations of all four threatened species of kiwi in New Zealand, and the experimental approach used has wider application in management of other threatened species.

Optimizing release strategies: a stepping‐stone approach to reintroduction

“…Chauvenet et al, 2010;Collazo et al, 2013;Helmstedt & Possingham, 2016;, few have evaluated how variation in release site characteristics can be exploited to reduce post-release effects and increase establishment success in metapopulation restoration efforts. For many bird translocations, techniques of temporarily or permanently 'marooning' populations on predator-free islands, generally outside the indigenous range of the species, have been used in a metapopulation context for recovery (Robertson et al, 2011;Jones & Merton, 2012;Parker, 2013). For many bird translocations, techniques of temporarily or permanently 'marooning' populations on predator-free islands, generally outside the indigenous range of the species, have been used in a metapopulation context for recovery (Robertson et al, 2011;Jones & Merton, 2012;Parker, 2013).…”

Conservation physiology can inform threat assessment and recovery planning processes for threatened species

“…One of New Zealand's major conservation efforts, Operation Nest Egg (ONE), has depended primarily on physiological data to inform its research protocol (Colbourne et al 2005, Holzapfel et al 2008). Kiwi reproduction is unique amongst birds and characterized by large egg sizes (taking up to 15 to 20% of the female's body cavity), rapid egg development (30 d from conception to laying), small clutches (generally a single egg), long incubation periods (74 to 84 d) shared by both male and female, and lack of parental-provided chick feeding (an external yolk sac provides nutrition for the first 10 d after hatching) (Colbourne 2002, Robertson et al 2011. Physiological data on kiwi reproduction led to development of the ONE protocol to boost the kiwi populations.…”

“…The protocol begins with removal of eggs from nests (located via radio telemetry of adult pairs), which are then incubated, hatched and the young reared in a secure ex situ environment (McLennan 1988, Colbourne et al 2005, Holzapfel et al 2008. Young are released into a predator-free zone to learn effective foraging techniques prior to release into the wild as adults (Robertson et al 2011). Genetics of the reared kiwis determine where they are released as adults to ensure genetic diversity and survival (Colbourne et al 2005, Le Duc et al 2015.…”

A two-stage translocation strategy for improving juvenile survival of Hawaiian monk seals

“…The associated uncertainties can only be resolved through strategic experimentation and project evaluation. The effort to conserve brown kiwis (Operation Nest Egg) is an excellent example, whereby methods were experimentally refined to achieve a significant net benefit to the species (Colbourne et al 2005, Robertson et al 2011). Adhering to a risk-averse decision framework limits the potential for over-commitment should failures occur.…”

“…However, when the cause of decline is not amen able to in situ treatment, creative and unconventional conservation schemes are required. A re markably successful ex ample is 'Operation Nest Egg', in which brown kiwis were collected and raised in captivity and on predator-free islands, then released back into their natal area once they had achieved a body size sufficient to escape predation by introduced carnivores (Colbourne et al 2005, Robertson et al 2011.…”