Justification of Red List Category
This species has a very small breeding range at only three known locations, which renders it susceptible to stochastic events and human impacts. Hence it is listed as Vulnerable. If invasive species, harvesting of chicks, bycatch in fisheries or other factors are found to be causing population declines, the species might warrant uplisting to Endangered.
There may c. 29,573 breeding pairs (Muñoz and P. Hodum unpubl. data), which would imply around 150,000 individuals.
Trends are unknown, although long-term breeding season monitoring on Robinson Crusoe and Santa Clara islands (2002-present) and Mocha (2010-2016) suggest stable populations. In addition, a comparison of burrow count data from 2003 and 2016 for all colonies in Juan Fernández indicates that burrow numbers have remained stable during that time (P. Hodum unpubl. data). Further research is needed to determine if introduced predators and herbivores on Robinson Crusoe Island, rats Rattus spp., dogs and feral cats (Felis catus) and harvesting of chicks on Isla Mocha, as well as fisheries bycatch are having any impact.
Ardenna creatopus is an east Pacific seabird that breeds only on Robinson Crusoe (a few thousand pairs in 1986 [Brooke 1987]; 2,750 occupied burrows in 2002 [Brooke 2004]; 10,055 burrows in 2016, of which up to 60%  may be occupied [P. Hodum unpubl. data]) and Santa Clara (2,000-3,000 pairs in 1991 [Brooke 1987] and 4160 breeding pairs in 2016 [P. Hodum unpubl. data]) in the Juan Fernández Islands, and on Isla Mocha (13,000-17,000 pairs [Guicking et al. 1999], but possibly up to 25,000 pairs [D. Guicking and P. H. Becker in litt. 1999]) off the coast of Arauco, Chile. Recent evidence suggests a small colony on Isla Santa Maria in the Gulf of Arauco, Chile (P. Hodum unpubl. data). These sites combined indicate around 30,000 breeding pairs, which would imply a maximum of 100,000 individuals (Brooke 2004). Following breeding, the species disperses northward along the west coast of South America towards North America (CEC 2005). There are also isolated records during the non-breeding period in Chilean Patagonia (Imberti 2005, C.G. Suazo in litt. 2016). The migration is evident by its increasing presence along the continental shelf from the Gulf of California in Mexico to British Columbia in Canada, during April and May each year. Numbers peak between August and October, followed by a rapid decline in November, as birds return to their breeding colonies (CEC 2005). Based on ship-based observations, and satellite tracking, Ardenna creatopus ranges from the northern Gulf of Alaska (from approximately 59.87º N) to southern Chile (to roughly 50.00º S); primarily over the continental shelf and slope regions (Mangel et al. 2012 in ACAP 2013). A specimen has also been taken from the Atlantic coast of Argentina (Mazar Barnett and Navas 1998) and there are records from New Zealand and Australia (Patterson 1991, D. Guicking and P. H. Becker in litt. 1999). Despite probable declines in the past, populations in the Juan Fernández group appear to have been more or less stable over the past 15 years (CEC 2005, P. Hodum unpubl. data), although the breeding population on Santa Clara Island increased by 40% following the eradication of European rabbits (Oryctolagus cuniculus) from the island in 2003 (P. Hodum unpubl. data). In contrast, populations on Isla Mocha may be declining owing to the effects of chick harvesting (CEC 2005), although breeding season monitoring between 2010-2016 suggested a stable population during that time (P. Hodum unpubl. data). Birds have been entangled in fishing gear near colonies and in the non-breeding range (Guicking et al. 1999, D. Guicking and P. H. Becker in litt. 1999, Mangel et al. 2012), and this potentially poses a major threat (Guicking et al. 2001, CEC 2005, Mangel et al. 2012).
Birds arrive at the colonies in early October-November. Eggs are laid in December, with fledging and dispersal in late April-late May (Guicking et al. 1999, P. Hodum unpubl. data). On Robinson Crusoe, nesting has been recorded in burrows scattered throughout badly eroded, generally sparsely vegetated but occasionally forested habitat at elevations of 50-390 m. On Santa Clara, the species breeds in scattered colonies in eroded terrain at elevations from 15-300m (Hodum and Wainstein 2003). On Isla Mocha, the colony is in forest (predominant tree Aextoxicon punctatum), with the highest burrow densities along mountain ridges and between the roots of old-growth trees up to 390 m (Guicking et al. 1999, D. Guicking and P. H. Becker in litt. 1999). It feeds primarily in offshore waters over the continental shelf but also in pelagic waters (Hodum et al. 2004), mostly on fish (sardines Strangomera bentincki and anchovies Engraulis ringens [Guicking et al. 2001]), squid and to a lesser extent, crustaceans (D. Guicking and P. H. Becker in litt. 1999). Birds breeding on Santa Clara demonstrate a diet dominated by fish, with squid comprising a smaller proportion of the diet (CEC 2005).
Interactions with fisheries potentially poses a major threat to this species (Guicking et al. 2001, CEC 2005, Mangel et al. 2012). Birds have been found entangled in fishing gear near colonies and in the non-breeding range (Guicking et al. 1999, D. Guicking and P. H. Becker in litt. 1999, Mangel et al. 2012). The distribution of longline commercial fishing activities overlap both spatially and temporally with the species’ wintering range over the continental shelf of North America, making the risk of interacting with the fishing fleet highly likely (CEC 2005). Bycatch mortality has been recorded in artisanal fisheries off the coast of Ecuador and Peru (Mangel 2012) which are poorly regulated and consist of a considerable number of small longline vessels whose overall impact may exceed that of large-scale fisheries. In Chile, capture by small vessels represents at least 76% of the overall bycatch of this species (Suazo et al. 2014, 2016).
Predation by cats Felis catus and Coatimundis Nasua nasua on Robinson Crusoe, and cats and dogs Canis lupus familiaris on Mocha (Guicking et al. 1999) represents another significant threat. The population of coatimundi appears to have declined from historical levels on Robinson Crusoe but predation is still being documented (P. Hodum in litt. 2017). On Isla Mocha, burrows excavated by dogs have been found, but there is no evidence of significant predation occurring (P. Hodum in litt. 2017). European Rabbits Oryctolagus cuniculus compete with shearwaters for burrows on Robinson Crusoe but were eradicated from Santa Clara in 2003 with a resultant 40% increase in the proportion of burrows occupied by breeding pairs (Hodum et al. 2017). Soil erosion by goats Capra aegagrus hireus and rabbits affects populations on Robinson Crusoe (Guicking et al. 1999, J. C. Torres-Mura in litt. 1999). At present, due to the highly restricted distribution of goats on the island, their impacts are minimal, in contrast to the pervasive presence of rabbits in all breeding colonies on Robinson Crusoe (P. Hodum pers. comm.). Cattle Bos taurus in one colony on Robinson Crusoe cause soil erosion and burrow collapses, but the core area of the colony is protected by a cattle-proof fence (Gladics and Hodum 2010); yet, cattle still impact burrows outside this area, although to a lesser extent (P. Hodum in litt. 2017). Both House Rats Rattus rattus and Brown Rats R. norvegicus occur on Isla Mocha and Robinson Crusoe, but their impacts are unknown (Hodum and Wainstein 2003). Stable isotope analyses of rat tissue suggest they are feeding at lower, terrestrial trophic levels, and no evidence has been found of eggs or chicks consumed by rats in burrows (P. Hodum in litt. 2017).
Chicks are harvested by islanders on Mocha in the fledgling season (March-May), with an estimated 20% of all chicks (3000-5000) taken in 1998 (Guicking et al. 1999, CEC 2005). More recently, due to enforcement of the prohibition of chick harvest begun in 2011, the magnitude of the chick harvest has decreased considerably, but illegal poaching still seems to occur most years (ACAP 2018). Quantitative estimates of harvest rates are difficult to obtain (P. Hodum pers. comm.). In 2018, illegal hunting was reported from Isla Mocha with c. 300 individuals killed in one incident (ACAP 2018).Plastic ingestion is widespread in the species, but there is no indication of what impact this currently has, or will have over the next three generations at either the individual or population level (P. Hodum in litt. 2017).
Conservation Actions Underway
The Juan Fernández Islands were designated as a national park in 1935 (protected from 1967) and a UNESCO Biosphere Reserve in 1977. The islands have been nominated for World Heritage listing (Hulm 1995). The Chilean government began a habitat restoration programme in 1997 (J. C. Torres-Mura in litt. 1999), which concluded in 2003. The distribution of breeding colonies on Robinson Crusoe and Santa Clara was determined in 2002-2006 and resurveyed in 2016, while Mocha was surveyed in 2009 and again in 2016. The colony on Mocha is within a national reserve, which has had a management plan since 1998 and two reserve guards (Guicking et al. 1999, J. C. Torres-Mura in litt. 1999). Harvesting of chicks is illegal under Chilean law (Guicking et al. 1999), although this was unenforced until 2011. Since 2011, the park guards have worked with the federal police to enforce the prohibition on chick harvesting. In Canada, Ardenna creatopus was assessed as Threatened in 2004 (COSEWIC 2013). In 2005, the CEC published the North American Conservation Action Plan for the species (CEC 2005). In 2008, Canada released a recovery strategy for Ardenna creatopus (EC 2008). Oikonos Ecosystem Knowledge has worked on the Juan Fernández Archipelago since the 2001–2002 breeding season, monitoring annual reproductive success and predation rates, evaluating threats to the population, and undertaking conservation actions such as the construction of fences to exclude cattle and predatory mammals from colonies, and the restoration of colonies through planting of native plant species within protective exclosures (P. Hodum pers. comm.). Satellite and GPS tracking has been used to determine foraging areas of breeding birds from both Juan Fernández and Mocha, migratory routes and wintering areas and potential interactions with fisheries (Mangel et al. 2012, Oikonos unpubl. data). At-sea observer programmes have been used to monitor bycatch around Mocha, in small-scale Peruvian fisheries and on some commercial fisheries in Chile (Mangel et al. 2012, Albatross Task Force-Chile unpubl. data, Oikonos unpubl. data). Community-based education and conservation programmes have been underway since 2002 on Robinson Crusoe (CEC 2005, P. Hodum pers. comm.) and since 2010 on Mocha (P. Hodum pers. comm.).
Conservation Actions Proposed
Remove all introduced mammals (D. Guicking and P. H. Becker in litt. 1999). Conduct quantitative assessment of population-level impacts of chick harvesting and reduce chick harvesting (Guicking et al. 1999). Expand the scale of habitat restoration through the planting of native plant species in and around breeding colonies. Assess the threat posed by the fishing industry, especially in Chilean waters (Guicking et al. 2001) and along migration routes, particularly in Peruvian waters. Expand population monitoring programme for Juan Fernández and Mocha breeding populations. Clarify the severity of threats faced in the non-breeding range. Build capacity for research and at-sea monitoring in Mexico. Expand and maintain community-based education and conservation programmes on Robinson Crusoe and Mocha.
48 cm. Large, dull shearwater. Dull greyish-brown head and upperparts. Thinly barred sides of head and neck becoming mottled towards sides of breast. Brownish mottling continues down flanks to merge into bolder brownish lower belly, undertail-coverts and thighs with slight pale mottling. Rest of underparts dull white. Dark mottling on underwing, especially in axillaries, over pale background. Pale pink feet. Yellowish bill with dark tip. Plumage varies between paler and darker morphs. Similar spp. Wedge-tailed Shearwater P. pacificus is smaller and more slender with narrower wings, longer tail and thin dark bill.
Text account compilers
Martin, R., Moreno, R., Stuart, A., Butchart, S., Clay, R.P., Anderson, O., Fjagesund, T., Calvert, R., Frere, E., Hermes, C., Lascelles, B.
Suazo, C.G., Morgan, K., Torres-Mura, J., Guicking, D., Becker, D., Hodum, P.
BirdLife International (2020) Species factsheet: Ardenna creatopus. Downloaded from http://www.birdlife.org on 04/12/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 04/12/2020.