Assessing the effectiveness of rehabilitation for management of an endangered seabird, the Yellow-eyed Penguin

Rehabilitation of wildlife can be a meaningful conservation technique if rehabilitated animals contribute to the breeding population. Endangered Yellow-eyed Penguins (<i>Megadyptes antipodes</i>) are declining on South Island, New Zealand, where modelling published in 2017 predicted their extirpation by 2043. Four management plans dating back to 1989 have been implemented in attempts to mitigate threats. The first three plans overlooked rehabilitation whereas the most recent, published in 2020, regarded rehabilitation as essential to save the South Island population. We assess the outcome of four decades of management of Yellow-eyed Penguins at Moeraki, southeast South Island, by Penguin Rescue, a volunteer conservation organisation. Here, nest numbers have fluctuated but overall increased at a long-term annual average of 5%. Their proportion of the southeast South Island total rose from 1% (six of about 453 nests) in 1982 to 26% (43 of about 166 nests) in 2021. Since 1986 our management has included rehabilitation of all juvenile or adult Yellow-eyed Penguins we encountered locally with life-threatening injuries, emaciation or sickness, with 590 of these marked before release from our rehabilitation facility. We accounted for the effect of rehabilitation on nest numbers by subtracting the number of rehabilitated female breeders and their female descendants from the total number of female breeders. Without rehabilitation nest numbers at Moeraki in 2021 probably would have remained similar to the initial six nests in 1982 instead of the seven-fold increase through four decades. We conclude that rehabilitation is an effective management technique for this species.