Justification of Red List Category
This species is classified as Vulnerable because it is restricted to one extremely small island group and hence is susceptible to stochastic events and human activities. Population trends are not clear, but if it is shown to be undergoing any decline, as is happening in some congeners, the species may warrant uplisting to a higher threat category.
The population was estimated at 23,250 breeding pairs in 1985-1986; 19,000 on North-East Island, 3,500 on Broughton and 750 on the Western Chain islets (Marchant and Higgins 1990). In 2000, 23,683 pairs were counted on North-East Island and 4,737 on Broughton Island, while an additional 381 pairs were estimated to breed on the Western Chain (Amey et al. 2001). The 2008 survey produced counts of 16,470 pairs on North-East Island and 3,375 pairs on Broughton, suggesting that the species had experienced a poor breeding year in line with that observed for the other seabird species present. Repeat surveys in 2010 found 21,167 and 4,358 pairs. A survey in 2013 found 20,716 pairs on North-East Island and 4,433 pairs on Broughton (Hiscock and Chilvers 2016), suggesting that there are at least c.50,300 mature individuals. Assuming that 80% of adult birds engage in breeding each year there should be a total of c.63,000 mature individuals.
Surveys suggest that the population on North East and Broughton Island is stable (Amey et al. 2001, Mattern et al. 2009, Hiscock and Chilvers 2016).
Eudyptes robustus breeds on the Snares Islands (3 km2), 200 km south of New Zealand. The most recent survey in 2013, found 20,716 and 4,904 pairs on North-East Island and Broughton respectively (Hiscock and Chilvers 2016). There is also a small population (“fewer than 500 pairs”, Miskelly 1997) breeding on the Western Chain (c.5 km west of North East Island). It appears that penguins’ breeding phenology on the Western Chain is delayed by 6-weeks and that minor morphological differences to the main island exist (Miskelly 1997). At-sea dispersal is largely limited by the subtropical front (STF), a hydrographic feature that separates warmer subtropical from cooler subantarctic water, with penguins foraging predominantly in warmer regions of the Tasman Sea and the eastern Indian Ocean (Mattern 2013, Thompson 2016).
This species nests in dense colonies, of usually between 50 and 500 pairs (mean 198, range 1-1,246; Amey et al. 2001), mostly under the forest or dense scrub on North-East Island, but otherwise in the open (Mattern 2013). Chicks are fed on krill (60%), fish (30%) and squid (10%), though there are indications that fish and squid play a more important role in the diet of adults (Mattern et al. 2009). In the breeding season the species forages predominantly in the Subtropical Convergence Zone. During the incubation stage penguins range up to 200 km east, while during chick rearing the birds remain within an 80 km radius to the north of the Snares Islands (Mattern 2013). During winter migration the birds venture up to 3,500 km westwards into the Indian Ocean, principally remaining in subtropical waters north of 45°S (Thompson 2016). There is only one observation of a Snares Penguin interbreeding with another species of Eudyptes (E. sclateri), although interbreeding is more common amongst other eudyptids (Morrison and Sagar 2014).
The main threats are commercial fisheries, oceanographic changes, and oil spills (Mattern 2013). The Snares Islands are the site of a large squid fishery, which affects the Snares Penguin through resource competition (Ellis et al. 1998; Crawford et al. 2017) while bycatch in set net fisheries is also a known source of mortality (Crawford et al. 2017). Both of these threats have the potential to drive significant declines, but do not seem to be doing so at present.
There are no introduced predators on the Snares Islands and consequently the possibility of the accidental introduction of mammals is a continual concern (Mattern 2013). The probability of colonisation is low due to the biosecurity measures in place and rats or mice, the most likely species to colonise appear to have minimal impact on other Eudyptes species. However, other members of the genus in the region have undergone considerable long-term declines (E. sclateri, E. chrysocome), perhaps due to oceanic warming and the associated change in distribution of prey species (Ellis et al.1998, Morrison et al. 2015), hence continued monitoring of the population is essential.
Conservation Actions Underway
The Snares Islands are a Nature Reserve and part of a World Heritage Site declared in 1998. Landing is by permit only (D. Houston in litt. 2008). Population surveys have been conducted at 5-year intervals since 2000.
Conservation Actions Proposed
Turn World Heritage Site territorial seas (out to 12 nautical miles) into a marine reserve and restrict all fishing (B. Weeber in litt. 2000). Recognize 100-km radius around Snares Islands as a Marine Important Bird Area Seaward Extension of breeding colonies (Forest and Bird 2014). Collect more information on diet composition and life history parameters.
60 cm. Medium-sized, yellow-crested, black-and-white penguin. Dark blue-black upperparts, head, neck. White underparts. Bright yellow, thin stripe from above eye to form drooping, bushy crest behind eye. Bare pink skin at base of large red-brown bill. Similar spp. Erect-crested Penguin E. sclateri is taller with erectile, bushy crests. Fiordland Penguin E. pachyrhynchus lacks pink bare skin at base of bill, crest feathers usually shorter, whitish stripes often on cheeks.
Text account compilers
Seddon, P., Allinson, T, Taylor, J., Webster, T., van Heezik, Y., Pearmain, L., Martin, R., Calvert, R., Benstead, P., Ellenberg, U., Mahood, S., Mattern, T., McClellan, R., Moreno, R.
Houston, D., Morrison, K., Mattern, T., Webster, T., Ellenberg, U., Sagar, P., Hiscock, J., McClelland, P., Bell, B., Garcia Borboroglu , P., van Heezik, Y., Weeber, B.
BirdLife International (2021) Species factsheet: Eudyptes robustus. Downloaded from http://www.birdlife.org on 16/01/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/01/2021.