Foraging plasticity of yellow-eyed penguins (Megadyptes antipodes) in their subantarctic range

Foraging behaviour is crucial to the breeding success for marine predators, including seabirds. Yellow eyed penguins (Megadyptes antipodes) are central-place predominantly benthic foragers around mainland New Zealand. The mainland population of this iconic species is declining, with changes in the marine environment a suspected cause, in particular, warming water and poorer foraging success. Here, we undertook a detailed foraging study of the ancestral subantarctic population which is genetically separate from the northern population. Over two breeding seasons, we collected GPS logs from 94 deployments on 75 breeding yellow 1 -eyed penguins foraging from Enderby Island, AucklandIslands, New Zealand. Birds foraged up to 47 km from shore, more than twice as far as yellow-eyed penguins in many areas around mainland New Zealand. Foraging area size and maximum range (distance from shore) were larger in a year of greater breeding effort (2016), and also for females, and birds undertaking pelagic foraging trips. Differences in foraging behaviour are likely influenced by local bathymetry, environmental conditions, and individual preference. Despite comparable bathymetry in some areas, the southern population shows greater foraging plasticity than seen in the northern population, implying foraging conditions may be less restricted in the subantarctic. However, previous studies have shown breeding success at the Auckland Islands is inconsistent, and differing foraging behaviour between years indicates foraging conditions are likely variable. Prey availability and foraging success are also expected to be affected by warming water, with implications for future breeding success particularly from the effects of climate change and El Niño Southern Oscillations (ENSO).