• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
This species has a large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence does not approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is relatively small, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
The species was previously estimated to number 1,900-2,000 birds with c.200 in Northland, c.700 in the Volcanic Plateau, c.400 in the Hawkes Bay, c.150 in Wairarapa and c.400 in Manawatu (Heather and Robertson 1997). More than 750 were counted at Rotorua lakes alone in 2018 (J. Innes in lit. 2022). The population trend was believed to be stable in 2008 and 2012 (Miskelly et al. 2008, Robertson et al. 2013) and to be increasing at a rate of more than 10% over three generations in 2016 and 2021 (Robertson et al. 2017, 2021). For this reason, the population size is now thought to be higher than that estimated in 1997. The estimation of 1,000-5,000 mature individuals made by Robertson et al. (2017, 2021) is therefore followed here, but with a best guess of 2,000-4,000 mature individuals.

Trend justification
The population was formerly precautionarily suspected to be in decline owing primarily to habitat loss and modification and the impacts of human disturbance and introduced predators, however the species appears to be now stable or increasing (Robertson et al. 2017, 2021); for example, it has recently recolonised Southland (Petyt 2013, eBird 2021) and the population in the Rotorua Lakes area (a significant portion of the global population) has been increasing steadily with 364 individuals in 1985, 572 in 2011 (Sachtleben et al. 2014) and 757 in 2018 (J. Innes in litt. 2022).

This species is endemic to New Zealand. The remaining population is largely restricted to North Island although it has recently recolonised South Island (Petyt 2013, eBird 2021).  Numbers appear to be stable or increasing globally (Marchant and Higgins 1990, Robertson 2013, 2017, 2021) although some threats may continue to cause local declines. The reason for the rapid decline and extinction on South Island in the 19th century is not known.

It inhabits small bodies of freshwater such as sand-dune lakes and lagoons and larger inland lakes with shallow, sheltered inlets (Marchant and Higgins 1990, Heather and Robertson 1997). It also uses "artificial" habitats such as farm ponds and dams and oxidation ponds. It usually builds its nest on emergent vegetation at the water's edge, floating but attached to vegetation or overhanging branches; as such, it is easily broken up by wave motion or swamped (Marchant and Higgins 1990). It feeds predominantly on aquatic invertebrates, mostly insects and larvae, but sometimes fish and freshwater crayfish (Heather and Robertson 1997). Little is known about the species's life history or population dynamics.

Threats include the drying of dune lakes, destruction of nesting habitat, increasing vegetation, increased human activity on waterways, especially boat traffic, and predation by introduced rats Rattus spp. and mustelids Mustela spp., especially when nesting (Marchant and Higgins 1990, G. A. Taylor in litt. 1994, Sachtleben et al. 2014), although the overall population is now increasing (Robertson et al. 2017, 2021) such that they are likely to be causing declines only locally. The species is intolerant of disturbance by people on foot (Sachtleben et al. 2014). Nests are prone to boat wash caused by recreational boating, which occurs on many occupied lakes during the breeding season (K. Owen in litt. 2012). Low breeding success is achieved on large waters, possibly owing to fluctuating water-levels, wave action and disturbance by other species. Breeding success on dune lakes, farm dams and the sheltered arms of lakes appears to be higher (Marchant and Higgins 1990, K. Owen in litt. 2012), and increases in the number of water storage dams may be driving increases in this species's population in some areas (K. Owen in litt. 2012).

Conservation and Research Actions Underway
Infrequent, region-wide surveys have been undertaken to monitor some key population changes, e.g. the five-yearly census of the Rotorua lakes population. Predator control operations since c.2002  included the use of bait stations to control numbers of brown rats Rattus norvegicus around the shoreline of Lake Tarawera at the Tarawera settlement, which has led to a doubling of the local P. rufopectus population (Sachtleben et al. 2014).

Conservation and Research Actions Proposed
Regularly monitor population changes throughout its range. Carry out research into the species's life history and population dynamics. Quantify the effects of introduced predators on breeding success.

29 cm. Small, dark grebe. Blackish head with fine, silver feathers. Pale yellow eye. Dark, chestnut foreneck and breast. Black-brown upperparts. Paler non-breeding plumage. Similar spp. Hoary-headed Grebe P. poliocephalus is lighter and less red. Australian Little Grebe Tachybaptus novaehollandiae is smaller. Voice Silent except for chattering calls in breeding season.

Text account compilers
Berryman, A.

Contributors
Bell, B.D., Innes, J., Owen, K., Robertson, H.A. & Taylor, G.A.

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Recommended citation
BirdLife International (2024) Species factsheet: New Zealand Grebe Poliocephalus rufopectus. Downloaded from https://datazone.birdlife.org/species/factsheet/new-zealand-grebe-poliocephalus-rufopectus on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 23/12/2024.