Significant decline of endangered Antipodes Island penguins: Is extreme weather an additional impact?

Abstract

Worldwide, most crested penguin species (Eudyptes spp.) are in decline. New Zealand's subantarctic Antipodes Islands are of international significance for erect‐crested (Eudyptes sclateri) and rockhopper (Eudyptes filholi) penguins. Between 1995 and 2011, a 23% decline was recorded in the two penguin species on the Antipodes Islands. In October 2014, nest abundance counts on Antipodes Island were undertaken to determine if this decline was continuing, particularly in light of a significant storm event that hit the Antipodes area in January 2014 causing massive landslides during the penguin breeding season. All penguin colonies ground counted in 2011 were preferentially ground counted in 2014 or, if time or weather did not allow, were checked with binoculars to confirm colony presence or absence. Seventy‐three per cent of the colonies and the equivalent of 82% of all nests counted in 2011 were recounted in 2014. Overall, there was a 19% decline in erect‐crested penguin nests between 2011 and 2014. Rockhopper penguins showed a slight increase (2.6%). Landslides affected 11% of the main islands’ land area and 44% of surveyed nesting colonies. Erect‐crested penguin colonies with approximately 75% or greater of their area impacted by landslides showed a significantly greater decline than unaffected or only partially impacted colonies. Landslides showed a minimal effect on rockhopper nest numbers. There continues to be a significant decline of erect‐crested penguins at the Antipodes Islands. An increasing occurrence of extreme weather events are predicted with climate change and have the potential to increase land‐based flooding and landslides, adding additional impacts to terrestrial breeding marine species. Greater understanding of what is causing erect‐crested penguin decline is needed to prevent this endangered species from extinction.

The breeding biology of erect-crested penguins, Eudyptes sclateri: Hormones, behavior, obligate brood reduction and conservation

“…Twenty-four years on, sadly, the situation remains unchanged: the very few studies conducted since then have been involved mostly with just counting the numbers of erect-crested penguins breeding on the Bounty and Antipodes Islands south-east of New Zealand. These studies have documented further drastic declines in the population of erect-crested penguins on the Antipodes Islands [ 2 , 3 ] from those that we had observed in 1998 [ 4 , 5 ]. Findings from our 1998 research were presented in papers at three conferences [ 6 – 8 ] and a summary derived from our data is given in Davis [ 5 ].…”

“…The accuracy of our counts at Anchorage Bay, Stella Bay and Reef Point was very high. These three locations were also censused in 2011 [ 2 ] and 2014 [ 3 ] using comparable methods and at a similar time of the year/breeding cycle ( Table 4 ). It is clear that the downward trend in numbers of breeding erect-crested penguins continues, with numbers of active nests of breeding penguins reducing by approximately one-third over a two-decade period in this subsample of the population on Antipodes Island.…”

“…Nevertheless, it seems likely that climate change is negatively impacting erect-crested penguins breeding on the Antipodes Islands. Increased storm frequencies over the past decades likely contributed to an increased occurrence of landslips, especially in the south of Antipodes Island, which wiped out parts of colonies and killed penguins attending their nests [ 3 ]. Additionally, there is clear evidence that eastern rockhopper penguins, which also breed on the Antipodes Islands, have experienced a massive population crash since the mid-20 th century [ 57 , 58 ], attributed largely to reduced oceanic productivity [ 59 , 60 ].…”

Earthquake impacts on a protected pinniped in New Zealand

“…However, disaster‐induced changes to habitats can also have long‐term impacts on wildlife populations (Jolly et al, 2022). For example, nest counts in colonies of erect‐crested penguins ( Eudyptes sclateri ) on the Antipodes Islands in October 2014 showed significantly greater declines in the numbers of nests in breeding areas impacted by storms in January 2014 compared with colonies that were unaffected or only partially impacted (Chilvers & Hiscock, 2019). The loss of habitat and resources likely also explains why bald eagles ( Haliaeetus leucocephalus ) and peregrine falcons ( Falco peregrinus ) failed to breed on an Alaskan island following a volcanic eruption (Williams, Drummond & Buxton, 2010).…”

“…However, disaster-induced changes to habitats can also have long-term impacts on wildlife populations (Jolly et al, 2022). For example, nest counts in colonies of erect-crested penguins (Eudyptes sclateri) on the Antipodes Islands in October 2014 showed significantly greater declines in the numbers of nests in breeding areas impacted by storms in January 2014 compared with colonies that were unaffected or only partially impacted (Chilvers & Hiscock, 2019).…”