Chiaradia A. & Nisbet I.C.T. (2006) Plasticity in parental provisioning and chick growth in Little Penguins Eudyptula minor in years of high and low breeding success. ARDEA 94 (2): 257-270

We measured parental care (attendance patterns, foraging trip durations and meal sizes) and chick growth patterns in 45–54 pairs of Little Penguins Eudyptula minor at a breeding colony in southeast Australia during five breeding seasons. Chick survival and productivity were ‘good’ in two years, ‘bad’ in two years and intermediate in the fifth; these differences probably reflected changes in food availability. In ‘bad’ years, parents lengthened foraging trip durations from 1–2 days to 2–5 days, and shortened the length of the guard period by 25%. Meal sizes varied strongly with chick age, but were reduced only slightly in the ‘bad’ year and varied only slightly with the number of chicks in the brood and with the number of parents visiting the nest. Hence, food intake by chicks depended mainly on the frequency of feeds rather than on meal size. Chicks responded to reduced provisioning rates both by reducing mass growth (‘imposed’ response) and by delaying development (‘induced’ response). The chicks’ responses were primarily ‘imposed’ during the period of rapid growth (days 13–35), but were mixed and more varied later in the period of development. The ability of Little Penguins to adjust their foraging behaviour to reduced food availability is probably constrained by their short foraging range (< 20 km) and their nocturnal behaviour at the breeding colony, which limits foraging trip durations to discrete numbers of days.