|Scientific Name:||Procellaria westlandica|
|Species Authority:||Falla, 1946|
|Red List Category & Criteria:||Vulnerable D2 ver 3.1|
|Reviewer(s):||Butchart, S. & Symes, A.|
|Contributor(s):||Baker, B., Tennyson, A., Waugh, S. & Wilson, K.|
|Facilitator/Compiler(s):||Black, A., Calvert, R., Martin, R, McClellan, R., Stattersfield, A., Sullivan, B., Taylor, J., Anderson, O.|
This species qualifies as Vulnerable because it is restricted to one very small area when breeding, rendering the population highly vulnerable to stochastic events and other potential threats.
|Range Description:||Procellaria westlandica breeds in the densely forested coastal foothills at Punakaiki, South Island, New Zealand (Best and Owen 1976). In 1958, the population was estimated at 3,000-6,000 birds, in 1972, 6,000-10,000 birds, and in 1982, 1,000-5,000 pairs (Marchant and Higgins 1990). In 1974, however, only 818 occupied burrows were located (Best and Owen 1976). Recent estimates put the total population at fewer than 20,000 birds, and c.4,000 pairs (Heather and Robertson 1997, Adams 1998, Taylor 2000, ACAP 2009). Population modelling suggests a decline in numbers since 1985 (Freeman and Wilson 2002). It migrates in summer to central Pacific and eastern New Zealand waters, the east coast of Australia and off South America (Marchant and Higgins 1990, Brinkley et al. 2000), and is regularly recorded off the coast of Chile extending into the South Atlantic to the east of Tierra del Fuego (Spear et al. 2005). A large number were recorded in the area of the Golfo de Penas (400 individuals) and Canal Messier (850 individuals), Aisen, Chile, and all in heavy primary moult (Fraser 2009), potentially representing 10% of the world population of this species (Fraser 2009).|
Native:Chile; New Zealand
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population numbered c.20,000 individuals (roughly equivalent to 13,000 mature individuals) in 1982 and has remained stable, with c. 2,000 pairs breeding annually. The most recent population study has produced an estimate of 2,827 annual breeding pairs (95% CI: 2,143-3,510) (B. Baker in litt. 2012). Scattered burrows exist throughout the 16-km2 breeding area and populations in these areas may have been underestimated by up to 10%. On the basis of this information, the breeding population is not thought to exceed 4,000 annual breeding pairs (B. Baker in litt. 2012). Based on this upper estimate of c.8,000 birds breeding each year, and assuming that 25% of breeding age birds may skip breeding in any one year (as derived from long-term data sets on similar species), there are probably c.10,700 mature individuals (B. Baker in litt. 2012), assumed to equate to a total population of c.16,000 individuals.|
|Habitat and Ecology:||
Behaviour The species is a colonial, winter breeder. Most eggs are laid in May, and hatch mostly in the last half of June. Chicks fledge from November to January (ACAP 2009). In any given year, a large proportion of the population skip breeding, however, there is no discernible pattern to this behaviour although it maybe linked with El Niño events (Waugh et al. 2006). Skipped breeders have lower survival rates, possibly owing to differences in the 'fitness' of individuals, although this could be biased by emigration. Juveniles return to the colony as young as three years, but the age of first breeding is six to seven years (Waugh et al. 2006). During chick-rearing, satellite-tracking data indicate foraging principally on the continental slope off the West Coast of South Island, with one trip undertaken through Cook Strait to the Chatham Rise east of South Island (ACAP 2009). Habitat Breeding They nest on densely forested hills at 20-250 m. Burrows are usually concentrated in areas where the ground is relatively open, and where take-off areas are close by. This is one of the few remaining petrels still nesting on mainland New Zealand, possibly due to more aggressively resisting attacks from land-based predators (Brooks 2011). Diet Fisheries waste is an important dietary component, perhaps forming more than half of solid food eaten during the hoki fishing season (Freeman 1998). Subsequent satellite tracking studies have suggested that dietary analysis over-estimates the amount of food scavenged from trawlers and that the species continues to forage over wider areas than those occupied by the hoki fishery. Even individuals known to forage at fishing fleets acquire a large proportion of their food elsewhere (Freeman et al. 2001, Freeman and Wilson 2002).
|Major Threat(s):||Introduced mammals and the native Weka Gallirallus australis prey on eggs, chicks and adults, goats trample burrows, and contribute to the erosion of subcolonies (Best and Owen 1976, Marchant and Higgins 1990, A. J. D. Tennyson in litt. 1994, Taylor 2000, Waugh et al. 2006). Mining and agriculture may have destroyed some available habitat but this has probably had little impact on the population as the birds breed on land too steep and difficult of access to be of interest to mining or farming (K.-J. Wilson in litt. 2008). The coastal plain between the colonies and the sea is rich in ilmenite and, for 20 years, mining of ilminite has seemed likely and the processing plant was placed on their major flightpath. It appears that mining will not proceed (K.-J. Wilson in litt. 2008, 2012). Birds are occasionally killed by flying into power pylons, and are attracted to lights and noisy machinery at dawn and dusk (Taylor 2000). Punakaiki is a growing tourist destination, and lights from newly built hotels may pose a minor threat to the petrels (K.-J. Wilson in litt. 2012). It is a bycatch species of tuna longliners in New Zealand and Australia (Heather and Robertson 1997), although the level of bycatch appears to be minimal (B. Baker in litt. 2012), and it is exposed to several longline fisheries off the coast of Chile. Birds regularly follow commercial trawlers and may be killed when nets are hauled (Taylor 2000). Interactions with Patagonian toothfish Dissostichus eleginoides vessels in the Humboldt Current System are also undocumented (ACAP 2009).|
Conservation Actions Underway
CMS Appendix II and ACAP Annex 1. The breeding site is within the Paparoa National Park. A proposal to designate the colonies as the Westland Petrel Special Area was approved in 1999, and restricts public access. A long-term study has been in place since 1969, covering social organisation, behaviour, breeding biology and aspects of population dynamics. A demographic study was undertaken between 1995 and 2003 (Waugh et al. 2006). Predator and herbivore control has been carried out in the main breeding colonies since 1990 (Taylor 2000).
Conservation Actions Proposed
Census all burrows every 10 years, and continue annual monitoring of study burrows, and band chicks and adults. Identify and minimise hazards to birds flying to and from the colony. Continue sustained predator control and monitoring of nests to identify predation events, and respond accordingly, and continue sustained control of browsing mammals, particularly goats and possums. Fence colony boundaries to exclude stock (Taylor 2000). Minimise the impact of tourist infrastructure through planning control (K.-J. Wilson in litt. 2008). Maintain vigilance in assessing seabird-fisheries interaction data in New Zealand and other areas to ensure that changes in fisheries operations, gear types and areas of activity do not lead to concomitant changes in bycatch (B. Baker in litt. 2012).
|Citation:||BirdLife International 2012. Procellaria westlandica. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 29 July 2015.|
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