Belinda Cannell

The largest colony of Little Penguins in Western Australia is located on Penguin Island, 50 km south of Perth, and the breeding performance of a nestbox subpopulation has been monitored for over 20 years. From our long term data set, high SSTs in April and May, both offshore and close to the colony, are correlated with fewer chicks per pair and lower masses of chicks at fledging. In the summer of 2010 and throughout 2011, the waters along the south-western coast of Western Australia were impacted by a record strength Leeuwin Current and above average sea surface temperatures. In 2011, the penguins breeding participation and success were the lowest observed since monitoring began. Less than a third of the average number of eggs was laid and only 10% of these resulted in successful fledglings. In addition, four times the average number of penguins was found dead from August-December 2011. The dead penguins were found on Penguin Island and along the coast, up to 400 km south of the colony. Autopsies revealed that many of the penguins had died from starvation. Diet composition studies revealed that whitebait, Hyperlophus vittatus, the major constituent of their diet in previous years, was absent in 2011. It is likely that the anomalous oceanographic conditions impacted the presence of the whitebait in the local coastal waters. However the construction of a boat ramp adjacent to the major whitebait nursery in 2010 may have also played a role. These data highlight the ability to use penguins as sentinels of climate change but also the difficulty in decoupling environmental and anthropogenic causes of change. The next step is to determine how resilient both the coastal ecosystem and this genetically distinct penguin colony are.

Little penguins from Penguin Island were found to either dive to shallow depths of 1-5m or to depths of 8-10m. As they use coastal bays that are also used extensively for water-based recreation, we hypothesise that both the shallow and deep diving penguins can potentially be disturbed or injured by watercraft. TDRs were attached to six little penguins, and the dive patterns and activity were described for the shallow and deep diving penguins separately. Shallow diving penguins executed >1200 dives per day with average dive duration of 10 seconds and spent one third of their day at sea underwater. Almost two thirds of their dives were to depths within the top 2m. The deep diving penguins executed fewer dives but of longer duration and thus spent approximately half of their time at sea underwater. These penguins had longer post-dive recovery. All penguins travelled in the top 2m and could spend >20 seconds within this depth. Both groups spent periods of 3 minutes to more than one hour at a time on the surface. Little penguins dive when they are approached by boats, and results of autopsies of little penguins showed many had injuries that were likely to be caused by watercraft. Penguin Island is part of a rapidly growing region with increasing human usage of the coastal waters. We urge state and local government authorities to develop management strategies to ensure the survival of this population of little penguins.

The rapid growth of urban areas near Little Penguin colonies on Penguin and Garden islands in Perth, Western Australia, potentially increases their exposure to various threats. To identify the possible range of threats at sea, the foraging ranges and diving behaviour of the penguins have been studied. From radio tracking Penguin Island penguins and satellite tracking those from both islands, we found they generally remained within a 20 km radius of their colony during breeding. Using time depth recorders, we found the penguins travelled in the top 2m, and some penguins preferentially dived within the top 4 m. The bays used by the penguins are also used extensively for recreational and commercial activities such as fishing, boating, water skiing and windsurfing. Results of autopsies of Little Penguins showed many had injuries that were likely to be caused by watercraft.

Little penguins on Penguin Island, Western Australia, have a protracted breeding season lasting from May to November/December. Peak numbers of eggs are laid in June and September/October and some pairs may lay two clutches of eggs in one year. The birds moult in December/January and depending on the timing of their breeding, may still be rearing chicks as they fatten during the premoult period. Some birds may abandon chicks in order to moult. The coordination of metabolism, moulting and reproduction and co-ordination of all these with season, probably involves endocrine systems. We therefore measured the circulating concentrations of prolactin, thyroxine (T4) and triiodothyronine (T3) during the annual cycle of little penguins, using the birds from the Penguin Island colony and Perth Zoo. Prolactin concentrations did not appear to be strongly associated with annual changes in photoperiod but increased during incubation and chick rearing. There were no differences between the sexes, but captive penguins had higher values than those in the wild. Prolactin values decreased when the penguins began to lose their feathers during the moult cycle. Changes in the concentrations of T4 and T3 were not associated with stage of the breeding cycle but increases were observed during the moult. In particular, T4 appears to play a significant role in the stimulation of feather growth, with values during the premoult phase that were 3-fold higher than the yearly average. We conclude that, for little penguins, thyroid hormones and prolactin may play important roles in coordinating the physiological changes associated with breeding and feather moult. The lack of difference between the sexes reflects their similar roles in chick rearing, and the difference between captive and wild birds probably reflects the nature of the food supply in these two environments.