KIWIKIU RECOVERY

MAUI'S MOST CRITICALLY ENDANGERED FOREST BIRD

The Kiwikiu (Maui Parrotbill; Pseudonestor xanthophrys) is a critically endangered Hawaiian honeycreeper endemic to the island of Maui. Once found across much of the islands of Maui and Moloka’i, the Kiwikiu is now limited to 30 km2 of wet rainforest on windward east Maui. Their historic range covered multiple forested habitat types from high elevation wet forests to lowland dry forests. Subfossils have been found down to 200 m in elevation in the Kahikinui region in southeast Maui and the fossil sites on Moloka‘i are at coastal dunes. 

Like many other native forest bird species, Kiwikiu are primarily threatened by non-native species, loss and/or alteration of habitat, and climate change. Wide-scale deforestation for agriculture and livestock grazing has reduced the amount of forest cover on the island of Maui to a fraction of prehistoric levels. The subsequent addition of invasive plant and animal species further eroded the extent of native forest and reduced forest quality throughout the island. Furthermore, introduced avian diseases restrict Kiwikiu to forests above 1200 m in elevation, above the elevational range of disease vectors; i.e. mosquitoes. As such, the current range of the species is constrained by the combination of the distribution of high quality native forest and disease vectors. The current range of the species is located on the windward slopes of Haleakalā Volcano from The Nature Conservancy’s (TNC) Waikamoi Preserve in the east to the Manawainui planeze in Haleakalā National Park.

Current Kiwikiu (Maui Parrotbill; Pseudonestor xanthophrys) species range (Total area = 29.92 km2) and land management areas. Also shown are the genetic sampling locations, including showing collection sites of initial captive individuals (east). Subpopulations, east and west, are based on analysis of genetic population structure by Mounce et al. (2015).

Species Status

Endangered. The first comprehensive population survey for Kiwikiu was done in 1980 as part of Hawai‘i Forest Bird Surveys. The population estimate at that time was 502 ± 116 individuals. While subsequent surveys have shown densities in certain portions of their range as similar to 1980, none have been able to conclusively show that the population is stable across its range. The recent 2017 range-wide study estimated Kiwikiu abundance at between 44 – 312 (95% CI; mean 157) individuals (analysis still in prep, not peer reviewed). While alarming, abundance estimates for the species have historically shown significant variability and the low precision of each estimate should not be ignored. However, overall abundance is realistically fewer than 312 and the population may be declining. Regardless of exact numbers, recent distribution surveys have suggested that their current habitat is “full”, with no room to expand.

Recommended Conservation Management

Data show a species in decline. Current rates of reproduction and survival will not sustain the population into the future. Population viability analysis predicts extinction of the species within 25 years. The forests that the Kiwikiu currently exists in are well protected: habitat management already includes removing ungulates and invasive species. Managers do not currently have the tools necessary to be able to mitigate the remaining threats in their current range (avian disease, vector and predator control on a landscape scale, weather). Climate change models predict that Kiwikiu habitat could decrease to 7 km2 on the windward slope by 2080-2100. The combination of all these factors and limitations make moving these birds to a new habitat (thus expanding their range) the most immediately viable option to secure their survival.

The U.S. Fish and Wildlife Service (USFWS) Recovery Plan (2006) calls for the creation of a second population of Kiwikiu. According to USFWS, the recovery strategy for the Kiwikiu centers on protection, restoration, and management of native high elevation forests on East Maui (Haleakalā), West Maui, and East Moloka’i. This includes ungulate monitoring and control, predator control, disease monitoring and control, captive propagation, and habitat restoration. Habitat restoration and reestablishment of a population on leeward East Maui is needed to promote natural demographic and evolutionary processes. Habitat restoration should eventually relink the remnant Kahikinui forest to other forests on East Maui. There is historically occupied habitat currently being restored on leeward east Maui for the benefit of Kiwikiu and other imperiled Hawaiian biota on Maui. This habitat is a mesic forest that appreciates lower annual rainfall forest than the habitat in the birds’ current range.

There are many reasons for using reintroduction as a conservation tool in a given species, but put in its simplest form, restoring a species to an area where it has been extirpated will increase the total number of individuals for that given species over time and reduce extinction risk. The release of such organisms back into historical habitats is known as a reintroduction. When moving threatened and endangered species where conservation is the main objective, these reintroductions are also considered conservation translocations.

Reintroductions have been widely used throughout conservation programs worldwide and the number of such efforts is growing exponentially each year. The increasing use of reintroductions is not unexpected due to the accelerating rate of global ecological change and the corresponding pressure on biodiversity.

Many of these reintroductions have been on islands, which is not unexpected given that islands hold a large percentage of our global diversity. Due to the inherent nature of island populations, these species do not have the luxury of large numbers of individuals that continental conservation programs might have and often rely on small numbers of founding individuals. There are many examples of successful and well-known island reintroductions around the world that started from low numbers of individuals. Some examples of these include but are not limited to:

  • The Echo Parakeet (Psittacula echo) in Mauritius which recovered from ~10 individuals to more than 550
  • The South Island Saddleback (Philesturnus carunculatus) in New Zealand which recovered from ~36 individuals to more than 2000
  • The Black Robin (Petroica travers) in New Zealand which recovered from ~5 individuals to ~200
  • The Laysan Duck (Anas laysanensis) in Hawai’i which recovered from 42 founders on a new island to a breeding population of more than 500
  • The Mauritius Kestrel (Falco punctatus) in Mauritius which recovered from ~4 individuals to more than 500
  • The Nihoa Millerbird (Acrocephalus familiaris kingi) in Hawai’i which has recovered from 50 founders on a new island to a breeding population of more than 160
Captive Breeding

The Kiwikiu captive population was initiated in 1997 and founding individuals were collected from the eastern subpopulation in 1999, 2001, and 2005. San Diego Zoo Global manages the conservation-breeding program at the Maui Bird Conservation Center and Keahou Bird Conservation Center in Hawai’i. Five genetic founders have composed the captive population. There are only 7-8 individuals that may be released into the wild. The relatively small number of breeding females and the unique life history characteristics (pair bonding, one egg per clutch, long juvenile dependency) of the Kiwikiu limits current breeding potential in captivity. Because of the low numbers and low genetic diversity of Kiwikiu in captivity, wild Kiwikiu will need to be used in the reintroduction.

Reintroduction

The creation of an additional population of Kiwikiu is a critical management action that is necessary to improve the long-term population viability of the species and is a high-priority action listed in the species’ recovery plan, and for USFWS, DLNR-DOFAW, and MFBRP. 

Short-term objective: to create a disjunct population of Kiwikiu, separate from the main source population, which survives through multiple years. 

Long-term objective: the newly established population of Kiwikiu to be self-sustaining, successfully breeding, and to achieve sufficient size to provide significant protection from extinction in case the source population is threatened or extirpated. Achieving this goal will require substantial resources, committed over a long period.

Site Selection

Selection of a suitable reintroduction site was based on a number of factors, including historical distribution of Kiwikiu, the need to promote natural demographic and evolutionary processes, establishment of a disjunct population to reduce extinction risk, and to increase the ecological breadth of the species to help buffer against climatic fluctuations. The selected site should fulfill the year-round requirements for the species to ensure that birds remain in the managed habitat (e.g. sufficient seasonal food resources, nesting and roosting sites). Site selection and subsequent management includes the evaluation of the species’ natural history requirements, vegetative analysis, physical qualities (area), elevation, elevational gradient, topography, soil characteristics, prevailing weather patterns, corridor potential, proximity to other conspecific populations, biological limiting factors (e.g., diseases, mosquitoes, predators, food availability, feral ungulates, alien competitors), anthropogenic threats, historical habitat modification and cultural practices of pre-contact Hawaiians, and current level of management and landowner cooperation and integration (habitat conservations plans, safe harbor agreements, etc.). 

Kiwikiu currently occupy roughly 20% of the identified recovery habitat on East Maui on the northern and eastern slopes of Haleakalā. 

The recovery habitat on West Maui and Moloka‘i is predominately fenced and ungulate-free, but much of the habitat lies below the 1,400 m elevation where mosquitoes become more plentiful and Plasmodium is able to complete its life-cycle. While the long-term goal for the recovery of the Kiwikiu may be dependent on establishing a second viable population in one or both of these areas, more work is needed to assess the current mosquito abundance and disease prevalence in the areas and potentially develop methods to reduce or eliminate this limiting factor before reintroductions can begin in those locations.

The western and southern slopes of Haleakalā offer the most immediate opportunity to create a disjunct second population and expand the range and population of Kiwikiu in the near term; therefore, the USFWS recovery plan identifies reintroduction to leeward Haleakalā as one of the high priority actions for Kiwikiu.

This area is sufficiently separated from the current population and creating an additional population would improve the conservation status of Kiwikiu by reducing the risk of extinction from demographic or environmental stochasticity. It would also serve as the founding population for an eventual connection to the current population through National Park owned lands to the east. 

The original mesic forests on these slopes were destroyed or severely degraded by ranching and feral ungulates over the past few centuries, which caused the local extinction of Kiwikiu. Some remnant forest exists on state-owned land within the Kahikinui Forest Reserve and Nakula Natural Area Reserve (NAR) and on land owned by the Department of Hawaiian Homelands. Restoration of this area has begun by the State of Hawai’i, MFBRP, Leeward Haleakala Watershed Restoration Partnership and partner agencies and when restored, these areas will support a mature mesic koa-‘ōhi‘a forest, which historical observations suggest was a prime habitat for Kiwikiu. Learn more about forest restoration for the Kiwikiu release here.

To learn more about the Kiwikiu release, read the Kiwikiu Reintroduction Plan here.

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