Justification of Red List Category
This species is listed as Vulnerable because it has a small population, which is undergoing a continuing decline owing to habitat degradation and the impacts of introduced predators.
The population is estimated to number 4,500-5,000 individuals, roughly equating to 3,000-3,300 mature individuals.
Analysis of wintering flocks indicates a slow decline over the last 40 years (Veitch and Habraken 1999), which is supported by preliminary results from a long-term demographic study (J. E. Dowding in litt. 1999).
Anarhynchus frontalis breeds in Canterbury and Otago, South Island, New Zealand. It is found on over 26 riverbeds, but is only common on 10. It winters mainly north of 38°S in the North Island. In the last 40 years, population counts have varied between 3,000 and 5,000 individuals (Sagar et al. 1999a), probably reflecting the difficulty in surveying the species (J. E. Dowding in litt. 1999), but the current best estimate is 4,500-5,000 birds (Riegen and Dowding 2003). Analysis of wintering flocks indicates a slow decline over the last 40 years (Veitch and Habraken 1999), which is supported by preliminary results from a long-term demographic study (J. E. Dowding in litt. 1999).
It breeds on braided riverbeds, and frequents sheltered estuaries and coasts over the non-breeding season. Nests are built within 250 m of running water, and are usually hollows in bare shingle, lined with more than 100 small pebbles (Marchant and Higgins 1993, J. E. Dowding in litt. 1999). It lays two eggs. Young usually begin to breed at two or three years of age (Marchant and Higgins 1993). Mark-recapture of almost 2,400 birds indicates that many live past 10 years of age (Davies 1997), the average adult life expectancy is c.5.4 years (Hay 1984). Diet comprises mostly mayflies and caddisflies, but is more general when rivers are in flood (Heather and Robertson 1997).
Breeding habitat is deteriorating, primarily from the encroachment of weeds as hydroelectric schemes reduce seasonal flushing of riverbeds (Marchant and Higgins 1993), and perhaps also owing to changes in the management of gravel extraction regimes (D. Melville in litt. 2012). Land intensification in the high country will have similar effects on reducing water flow, as well as increasing the concentration of nutrients in rivers, further encouraging weed growth (Rebergen 2011). The extent of predation by stoats Mustela erminea and cats has not been quantified, but is likely to be substantial, perhaps especially in the non-breeding season (Battley and Moore 2004). The recent illegal introduction of rabbit haemorrhagic disease has resulted in the localised switching of some predators to a diet containing proportionately more birds. Predation by Kelp Gulls Larus dominicanus may pose an increasing threat as they become more numerous in association with human activities (J. E. Dowding in litt. 1999). Increasing use of riverbeds for recreational purposes and floods are also threats (Marchant and Higgins 1993, A. Grant in litt. 1999). Water quality deterioration and disturbance pose threats at the species's wintering grounds in Auckland and Northland (Rebergen 2011). Further threats may include the conversion of coastal habitat for aquaculture, development of wind farms, and the spread of mangroves (D. Melville in litt. 2012).
Conservation Actions Underway
The species was shot for sport until 1940, when it became fully protected (Marchant and Higgins 1993). Research on the impact of predation and prey-switching is being undertaken. Predator control for Black Stilt Himantopus novaezelandiae protection benefits a small proportion of the population (J. E. Dowding in litt. 1999). Project River Recovery carries out habitat restoration and predator research in the McKenzie basin (A. Grant in litt. 1999).
20 cm. Stocky, pale grey plover, tip of black bill turned to right. Ash-grey crown, nape, upperparts. White underparts. Black band across upper chest thick in breeding male, thinner in breeding female, sometimes absent in non-breeding birds. Black frontal band above white forehead in male, absent in female. Juvenile breast-band absent, back feathers tinged with white. Voice Short, clear weet.
Text account compilers
Benstead, P., McClellan, R., Pilgrim, J., Mahood, S., Taylor, J., Khwaja, N.
Riegen, A., Melville, D., Grant, A., Dowding, J.
BirdLife International (2020) Species factsheet: Anarhynchus frontalis. Downloaded from http://www.birdlife.org on 30/09/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 30/09/2020.