Little penguin Eudyptula minor at Middle Island, Western Victoria : current status

We examined the status of the Little Penguin Eudyptula minor at Middle Island on the west coast of Victoria during the species' 1999/2000 breeding season. The vegetated upper surface of the island had 292 occupied burrows at a density of 0.02/m². Peak dusk arrival occurred in January with 502 penguins coming ashore during a one-hour period. Little Penguins at Middle Island displayed important differences in breeding ecology from penguins in other Australian colonies. Early breeding combined with heavier adult and chick weights resulted in high breeding success. However, as Middle Island is a popular destination for day visitors, during the 1999/2000 Little Penguin breeding season, tourism ·was found to cause detrimental effects, including deaths of some eggs and chicks. There are also concerns for the conservation of the Little Penguin colony as faxes or dogs may readily access the island.

Foraging behaviour and habitat selection of the little penguin Eudyptula minor during early chick rearing in Bass Strait, Australia

Knowledge of the foraging areas of top marine predators and the factors influencing them is central to understanding how their populations respond to environmental variability. While there is a large body of literature documenting the association of air-breathing marine vertebrates with areas of high marine productivity, there is relatively little information for species restricted to near-shore or continental-shelf areas. Differences in foraging range and diving behaviour of the little penguin Eudyptula minor were examined from 3 breeding colonies (Rabbit Island, Kanowna Island and Phillip Island) in central northern Bass Strait, southeast Australia, during the chick-guard stage using electronic tags (platform terminal transmitters, PTTs, and time-depth recorders, TDRs). Although there were large overall differences between individuals, the mean maximum foraging range (16.9 to 19.8 km) and mean total distance travelled (41.8 to 48.0 km) were similar between the 3 colonies, despite different bathymetric environments. Individuals from all 3 colonies selected foraging habitats within a narrow sea surface temperature (SST) range (16.0 to 16.4°C). While there were significant differences in mean dive depths (5.4 to 10.9 m) and mean durations (13.2 to 28.6 s) between the different colonies, the mean diving effort (vertical distance travelled: 936.3 to 964.3 m h–1) was similar. These findings suggest little penguins from the 3 colonies employ relatively similar foraging efforts yet are plastic in their foraging behaviours.

Range-wide phylogeography of the Little Penguin (Eudyptula minor): evidence of long-distance dispersal

The Little Penguin (Eudyptula minor), a colonial-nesting seabird that is widespread in New Zealand and southern Australia, has high dispersal potential but exhibits regional variation in morphology, coloration, and breeding phenology. We present a distribution-wide survey of mitochondrial DNA variation in the Little Penguin to document phylogeographic relationships and genetic structuring and to test for concordance with intraspecific taxonomy. Phylogeographic structuring was absent among Australian colonies (27 localities, 94 individuals), but the distribution of haplotypes among colonies was significantly nonrandom (ϕST = 0.110, P < 0.01). The Australian individuals exhibited close phylogenetic relationships with a subset of New Zealand birds (4 localities, 22 individuals), whereas the remaining New Zealand birds (20 localities, 106 individuals) were phylogenetically distinct, with ≥7% sequence divergence, and exhibited greater levels of genetic variation and geographic structuring (ϕST = 0.774, P < 0.05). These patterns are consistent with earlier suggestions of an origin in New Zealand followed by recent colonization of Australia and back-dispersal to New Zealand. Extinction and re-establishment processes may have been important factors in the development of genetic structuring across a range of spatiotemporal scales. The genetic data are consistent with suggestions that a single subspecies exists in Australia, but not with the subspecies distributions within New Zealand that have been suggested on the basis of morphology and coloration.

Little Penguin (Eudyptula minor) variability in south-eastern Australia

This research examined the ecological, morphometric and genetic variability of the Little Penguin (Eudyptula minor) between seven colonies in south-eastern Australia. Significant differences in breeding ecology and morphology were noted for birds between colonies. However, most colonies were genetically homogeneous with respect to each other, with the exception of the Kangaroo Island colony.

Benefits of group foraging depend on prey type in a small marine predator, the Little Penguin

Group foraging provides predators with advantages in over-powering prey larger than themselves or in aggregating small prey for efficient exploitation. For group-living predatory species, cooperative hunting strategies provide inclusive fitness benefits. However, for colonial-breeding predators, the benefit pay-offs of group foraging are less clear due to the potential for intra-specific competition. We used animal-borne cameras to determine the prey types, hunting strategies, and success of little penguins (Eudyptula minor), a small, colonial breeding air-breathing marine predator that has recently been shown to display extensive at-sea foraging associations with conspecifics. Regardless of prey type, little penguins had a higher probability of associating with conspecifics when hunting prey that were aggregated than when prey were solitary. In addition, success was greater when individuals hunted schooling rather than solitary prey. Surprisingly, however, success on schooling prey was similar or greater when individuals hunted on their own than when with conspecifics. These findings suggest individuals may be trading-off the energetic gains of solitary hunting for an increased probability of detecting prey within a spatially and temporally variable prey field by associating with conspecifics.

Conservation genetics of the little penguin: eudyptula minor

This first range-wide study of the ecology and systematics of the Little Penguin, Eudyptula minor, supported a single species model with two distinct groups and a New Zealand origin. Critical information collected on gene flow, connectivity and sex identification will greatly enhance conservation strategies for this iconic Australasian bird.

Determining the sex of Little Penguins (Eudyptula minor) in northern Bass Strait using morphometric measurements

In avian species with no obvious differences in plumage or body size between the sexes, such as penguins, discriminant function analysis (DFA) of morphometric measurements that display sexual dimorphism can provide a simple and rapid means of determining sex in the field. Like most other penguin species, the Little Penguin (Eudyptula minor) displays sexual dimorphism in bill shape and size. In the present study, discriminant functions (DFs) were developed for sexing adult Little Penguins at two colonies in northern Bass Strait, Victoria, Australia, and their accuracies were compared with those obtained previously in other parts of the species' range. Backwards stepwise DFA indicated that birds at Phillip Island can be sexed with an accuracy of 91% using a single measurement of bill depth (>13.33 mm classed as males). Similar analyses at Gibson Steps produced a DF incorporating bill length, bill depth and head length [although the model with the greatest accuracy when applied to birds from Phillip Island (91%) also contained only bill depth]. Published DFs derived in New Zealand had accuracies of 50–85% when applied to birds from Phillip Island and Gibson Steps, supporting earlier suggestions that DFs are not applicable across subspecies of the Little Penguin. In contrast, there was little difference between the accuracy of the DFs in the present study and that previously derived for the same subspecies in Tasmania when applied to birds from Phillip Island (89%) and Gibson Steps (92%). However, as the degree of variation in bill size within a subspecies is unknown it may still be prudent to derive colony-specific DFs.

Synchronized group association in little penguins, Eudyptula Minor.

Most seabirds form groups on land and at sea, but there is little information whether seabird groups are formed deliberately or randomly. We investigated whether little penguins formed groups composed of the same individuals when they crossed the beach each day over four breeding seasons (2001–2004) using an automated penguin monitoring system (APMS). We used an association matrix to determine the number of times any two birds crossed the APMS in the same group. The number of these group associations or ‘synchronized parade’ behaviour was determined for every possible pair of individuals, giving a total association value for each pair of birds during the postguard stage of the reproductive cycle. We concluded that a penguin group was composed of 5–10 individuals within 40-s intervals. Penguin groups were formed nonrandomly in years of high breeding success (2002 and 2003), but not in years of low breeding success (2001 and 2004). Age of birds was a significant factor in composition of groups. Little penguins with higher association values shared similar characteristics or ‘quality’, which in turn may increase the functional efficiency of their groups, especially if they are also foraging together. However, low association indices indicated that seeking the same associates was not a priority. It is costly for any animal to synchronize their attendance with the same individuals, so it could be beneficial to display synchronized parade behaviour in good breeding years but it could result in intraspecific competition for food during poor breeding years.

Sexing little penguins eudyptula minor using bill measurements

In Little Penguins Eudyptula minor there are no reliable plumage or body size differences that can be used visually to distinguish the sex of individuals. However, sexual dimorphism of morphometric measures has been noted, with males always being a little larger than females. In this study, differences between E. minor sexes at eight colonies in south-eastern Australia were determined statistically via discriminant function analysis (DFA) and through the utilization of DNA-based techniques developed for non-ratite birds. The DFA correctly determined gender in 91.1% of cases and molecular methods were 100% accurate. Our DFA success rate of classification is similar to that previously published for Little Penguins in Victoria. In this study statistically significant differences in mean bill depths and lengths were found between Little Penguin colonies at St Kilda, Phillip Island and Gabo Island, compared to colonies at Kangaroo Island, Granite Island, Middle Island and London Bridge. As birds in eastern populations (St Kilda, Phillip Island, Gabo Island) exhibit statistically significantly smaller beaks (bill depth and bill length), separate discriminant functions were investigated for each phenotypically distinct geo-spatial cohort. Interestingly, cluster analysis for bill length identified three groups: western (Kangaroo Island and Granite Island), eastern (St Kilda, Phillip Island and Middle Island) and the London Bridge Little Penguin colony, which constituted a separate group. We conclude that while there is a slight increase in DF power for colonies west of Cape Otway and for some specific colonies, colony-specific DFA is not required to identify the sex of Little Penguins in south-eastern Australia.

Contrasting genetic structuring between colonies of the world's smallest penguin, Eudyptula minor (Aves: Spheniscidae)

The Little Penguin, Eudyptula minor, is a seabird that nests in colonies throughout New Zealand and southern Australia. Individuals from different colonies in southeast Australia differ significantly in morphology and ecology, suggesting that some genetic structuring may exist among colonies. In contrast, the marking of individuals with flipper bands has revealed some, albeit infrequent, movement between colonies. To determine the extent of genetic structuring, we tested the null hypothesis of substantial gene flow within southeast Australia by examining patterns of genetic variation across seven colonies separated by up to 1,500 km. Phylogeographic structuring was absent for mitochondrial control region sequences (2–3 individuals per colony). Microsatellite allele frequencies at five loci and mitochondrial haplotype frequencies (50 individuals per colony) were also homogenous among the majority of colonies sampled, although two colonies at the western periphery of the sampling range were distinct from those to the east. The genetic homogeneity among the majority of colonies can be explained by low but consistent contemporary gene flow among them, or a recent founder event in Bass Strait following the last marine transgression. The genetic break towards the western end of the sampling distribution appears best explained by differences in sea surface temperature and, consequentially breeding phenology, the latter hindering genetically effective migration.

Influence of environmental conditions on foraging behaviour and its consequences on reproductive performance in little penguins

During the breeding season, seabirds are central place foragers and have to adapt their foraging behaviour in response to environmental variation to maximize efficiency and reproductive output. Due to its small size and swimming mode of transport, the little penguin (Eudyptula minor) is expected to be greatly susceptible to such fluctuations. The links between local-, meso- and macro-scale environmental conditions and inter-annual variation in foraging behaviour and reproductive performance of little penguins were investigated during three consecutive breeding seasons at two colonies in south-eastern Australia marked by contrasting oceanographic conditions. At a local scale, foraging effort was correlated positively with wind direction and negatively with wave height. At a regional scale, foraging effort of individuals from both colonies was negatively correlated with higher sea surface temperature (SST) off the Bonney Coast in the previous Austral summer, suggesting a weaker Bonney Upwelling event and a cascade of effects throughout the Bass Strait region. At a larger scale, the El Niño Southern Oscillation was also found to correlate with foraging behaviour, with lower foraging effort being observed during La Niña event. Although individuals increased their foraging effort during years with poorer conditions, they were not able to maintain high breeding success. In addition, peak egg-laying was found to coincide with a decrease in local SST and a peak of sea surface chlorophyll-a concentration. In conclusion, these results highlight how different environmental conditions could influence foraging behaviour and ultimately reproductive success of little penguins. It also showed that under certain circumstances, these individual strategies were not sufficient to cope with environmental variability.

Breeding success and traits of equal and unequal pairs of little penguins (Eudyptula minor) on Phillip Island during 2001-2008

According to life-history theory, individuals optimize their decisions in order to maximize their fitness. This raises a conflict between parents, which need to cooperate to ensure the propagation of their genes but at the same time need to minimize the associated costs. Trading-off between benefits and costs of a reproduction is one of the major forces driving demographic trends and has shaped several different parental care strategies. Using little penguins (Eudyptula minor) as a model, we investigated whether individuals of a pair provide equal parental effort when raising offspring and whether their behavior was consistent over 8 years of contrasting resource availability. Using an automated identification system, we found that 72% of little penguin pairs exhibited unforced (i.e., that did not result from desertion of 1 parent) unequal partnership through the postguard stage. This proportion was lower in favorable years. Although being an equal pair appeared to be a better strategy, it was nonetheless the least often observed. Individuals that contributed less than their partner were not less experienced (measured by age), and gender did not explain differences between partners. Furthermore, birds that contributed little or that contributed a lot tended to be consistent in their level of contribution across years. We suggest that unequal effort during breeding may reflect differences in individual quality, and we encourage future studies on parental care to consider this consistent low and high contributor behavior when investigating differences in pair investment into its offspring. Key words: attendance patterns, individual quality, meal size, parental care, reproductive costs, seabirds.

Little raven (Corvus mellori) as an egg predator of other bird species

 Little ravens were major predators of ground-nesting red-capped Plover and burrow-nesting Little penguin eggs. Ravens also congregated at the breeding sites of these two species to exploit eggs. As raven numbers increase with human habitation of land, their impact on other bird species needs to be monitored and managed.

Distribution and abundance of seabirds in Western Port, Victoria

The distribution, abundance and biomass of seabirds in Western Port, Victoria, were surveyed between April 1991 and August 1994. Individuals were counted along an 81-km series of transects from a boat at approximately monthly intervals. A total of 25 seabird taxa were recorded, of which 18 and 15 were common to those recorded by an earlier study in Port Phillip Bay and waters south of Phillip Island, respectively. The most numerous species by far was the Short-tailed Shearwater (Puffinus tenuirostris) followed by the Silver Gull (Larus novaehollandiae), Little Penguin (Eudyptula minor) and Crested Tern (Sterna bergii). Distribution within Western Port was not uniform, with pursuit divers such as cormorant and grebe species being recorded mostly in the shallow Eastern Arm. In contrast, surface-seizing (e.g. albatrosses), surface-plunging (e.g. Crested Terns), shallow-plunging (Australasian Gannet, Morus serrator) and pursuit-plunging (e.g. shearwaters) species predominated in the deeper Western Arm of Western Port. These species were also seasonally abundant, with peak numbers for most occurring in late summer–early autumn, which coincides with the reported influx of juvenile clupeoid fish into Western Port. Average biomass (686 ± 395 kg) comprised mostly Short-tailed Shearwaters, Little Penguins and Pied Cormorants (Phalacrocorax varius). Biomass density (8.5 kg km^–2) was similar to that reported for Port Phillip Bay (8.1 kg km^–2) but lower than off the southern coast of Phillip Island (9.9 kg km^–2).