Predicting onset and success of breeding in little penguins Eudyptula minor from ocean temperatures

As is the case for many seabirds, we found that the timing and breeding success of little penguins Eudyptula minor on Phillip Island, southeastern Australia, was associated with sea surface temperature (SST) variation. Using 31 yr of data (1968 to 1998), we examined the correlations between breeding variables and regional SST at different times of the year. The next 9 yr of data (1999 to 2007) were used to test the performance of our statistical predictive models. Egg-laying date, chick mass and the number of chicks fledged per pair were correlated with SST in the first 3 mo of the year prior to breeding, in slightly different ways. SST provided more accurate predictions of mean laying date (53% variance) than of chicks produced per pair (22%) or mean chick mass at fledging (16%). This model predicted an early egg-laying date, higher average chick mass at fledging and a higher number of chicks produced per breeding pair when SSTs in Bass Strait are warmer than average in March. The models presented predict that an increase in SST is likely to lead to a reversal of the trend towards later breeding and suggest improved growth of the colony of little penguins on Phillip Island, at least in the immediate future.