Southern rockhopper penguin Eudyptes chrysocome chrysocome foraging at Possession Island

The foraging ecology of rockhopper penguins was studied at Possession Island, southern Indian Ocean, by counting the number of birds departing from and arriving at colonies over the course of the day and by equipping three birds with time/depth loggers, one of which was recovered having recorded a total of 12 days foraging activity. Both the counts and the results from the diving behaviour showed that the birds foraged exclusively diurnally. Maximum dive depth was 66 m although most time was spent between 10 and 25 m, depths that did not accord with the published distribution of their principal prey as detected by nets and acoustics. Received: 29 March 1996/Accepted: 10 June 1996     

Semen characteristics and artificial insemination in rockhopper penguins (Eudyptes chrysocome chrysocome)

This work was performed as part of a multi-year study to determine the cause of the low fertility in captive rockhopper penguins (Eudyptes chrysocome chrysocome) and attempt to increase the fertility through artificial insemination (AI). Semen collection and characterization was performed on 14 male rockhopper penguins. The samples were evaluated for volume, sperm concentration, and sperm quality (motility, forward motility, viability, and morphology). There was a large variation between individuals and between collections for each individual. Mean volume of ejaculate was 0.24 ml. Mean concentration was 47.09 × 10(6) sperm/ml. Mean number of sperm per collection was 6.57 × 10(6). The mean motility was 49.4%. Mean forward motility was 1.7. Mean percentage of living sperm was 88.9%. Mean percentage of sperm with normal morphology was 69.4%. AI was performed on a total of 10 females using pooled semen samples. The birds were also allowed to naturally mate. Ten eggs were laid and three fertile eggs were produced, one of them hatched but died within 24 hr. Paternity testing was performed using 12 microsatellite loci, but unfortunately due to insufficient variability, the paternity of the chick and two embryos could not be determined.     

Pasteurella multocida infections in rockhopper penguins (Eudyptes chrysocome) from Campbell Island, New Zealand

During an investigation into the population decline of rockhopper penguins (Eudyptes chrysocome) on Campbell Island, New Zealand, avian cholera (Pasteurella multocida) was found in dead adults and chicks. An RNA enveloped virus was isolated from Ixodes uriae, a tick which commonly parasitizes rockhopper penguins on the island. It is not known whether this virus is virulent for penguins. No evidence was obtained to suggest that avian cholera was the principal cause for the decline in the rockhopper penguin population.     

Morphological aspects of the heart of the northern rockhopper penguin (Eudyptes chrysocome moseleyi ): possible implication in diving behavior and ecology?

We compared the heart morphology of the small, deep-diving northern rockhopper penguin to the hearts of small, shallow-diving and large, deep-diving penguin species. The rockhopper penguin had a heart larger than expected for its body mass, and its heart weight/body weight was significantly greater than in the larger Adélie penguin. We found the rockhopper's right ventricle weight/heart weight to be significantly greater than this relationship in both the larger chinstrap and Adélie penguins. The relationship of the right to left ventricular weights in the rockhopper heart is not different to that of the large, deepest-diving emperor penguin. A larger heart in the rockhopper penguin might be related to its diving behavior and ecology if it contributes to diving efficiency during foraging by increasing lung perfusion during surface recovery. This would lead to decreased surface time. Accepted: 20 May 2000     

Genetic evidence for three species of rockhopper penguins, Eudyptes chrysocome

The taxonomy of rockhopper penguins, Eudyptes chrysocome (Forster 1781), is contentious. Some authorities recognise three subspecies based on morphological differences and geographical separation of breeding populations while others suggest that morphological differences support classifying rockhopper penguins as two distinct species. The taxonomy of rockhopper penguins is of more than academic interest as breeding colonies worldwide have declined markedly in size since the 1930s and rockhopper penguins are currently listed as vulnerable by the IUCN. We compared the genetic distances between three mitochondrial gene regions from the three putative rockhopper penguin subspecies with the distances between various penguin sister species to clarify the taxonomy and systematics of rockhopper penguins. Genetic distances between the rockhopper penguin taxa, relative to other closely related penguin species, support reclassifying the three rockhopper penguin subspecies as species. Reclassification of rockhopper penguins as three species could result in their conservation status being upgraded from vulnerable to endangered.     

The diet of the Southern rockhopper penguin Eudyptes chrysocome chrysocome at Beauchene Island, Falkland Islands

The diet of the Southern rockhopper penguin at Beauchene Island, Falkland Islands, was studied in the early chick-rearing period by quantitative analysis of adult stomach contents. Juvenile squid (Teuthowenia sp.) comprised on average 21% by numbers (c. 1000 per sample) and 53% by weight; crustaceans contributed 79% by numbers (c. 4000 per sample) but only 45% by weight, and fish 2% by weight. Of the crustaceans only the euphausids Euphausia lucens (66% by numbers), E. vallentini (19%) and Thysanoessa gregaria (15%) were present in significant quantities, and all are swarming species characteristic of the Patagonian shelf epipelagic zooplankton. Comparison is made with the limited dietary data available from other studies, and rockhopper penguins are suggested typically to feed opportunistically on swarming or shoaling zooplankton (particularly euphausids and young squid) and small fish. Whereas the average weight of the stomach contents was 220 g, the biomass of the individuals originally ingested was estimated to total 800 g; the c. 3000 kj this represents is consistent with the likely energy requirements of adults making daily foraging trips to rear small chicks.     

Satellite tracking of male rockhopper penguins Eudyptes chrysocome during the incubation period at the Falkland Islands

The foraging patterns of ten male rockhopper penguins Eudyptes chrysocome from the Falkland Islands were recorded during the incubation period by using satellite telemetry. Irrespective of study site and year, two different foraging areas could be identified. Three foraging trips were directed towards the slope of the Patagonian Shelf c. 140 km to the northeast of the breeding colony and these trips had a duration of 11–15 days. The seven other rockhopper penguins travelled c. 400 km towards the edge of the Falkland Islands' waters; all these foraging trips followed an anti-clockwise direction and lasted 16–27 days. The calculated mean daily travelling speed, based on the time spent underwater and the distance covered between two positions, was significantly higher in birds travelling to the edge of the Falkland Islands' waters compared with those foraging at the shelf slope (4.4±1.6 km/h vs. 3.4±2.0 km/h, respectively). The consistent foraging patterns exhibited during the long trips may be linked to the Falklands current, allowing the penguins to reach remote areas while reducing their energy expenditure. Potential interactions between commercial fisheries and hydrocarbon exploration are discussed.     

Spatial and temporal variation in the provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi

As seabirds are central place foragers during breeding, their provisioning behaviour and their ability to face variable energy demand from the chicks is expected to vary with environmental conditions. The provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi was recorded over the chick‐rearing period at Kerguelen (KER) and Crozet (CRO) archipelagoes (two very distinct marine environments), using time‐depth recorders, or VHF transmitters coupled with an automatic recording station. No influences of the method have been found on the average foraging trip durations. Some previously undescribed short and multiple trips within a day were recorded using the automatic recording system. These multiple trips (6.8 h) were mostly performed with <5 days old chicks, a period during which feeding rates were the highest (1.1 meals per day), at both sites. During the brooding period, both KER and CRO females mainly performed daily trips of increasing duration (2 h longer at CRO) and at decreasing frequency. During the crèche compared to the brooding period, females from KER performed slightly fewer daily trips (0.6 per day) and more (<3 days) overnight trips, while females from CRO performed very few daily trips (0.1 per day) and more overnight trips, some of them being long trips lasting 5 to 29 days, mostly initiated during the transition between the brooding and the crèche periods. The result fit the hypothesis that long trips permit females to restore and/or maintain their body condition at more distant foraging places. It seemed that chick developement during the brooding period and environmental factors during the crèche period conditioned trip duration of females. Due to more long trips at CRO, the female feeding frequency was twice as high at KER than at CRO during the crèche period, while males participated in the feeding duties. Based on differences in female behaviour, we hypothesize that the male's contribution is likely to differ strongly from one site to another, and may buffer the possible decrease in female feeding frequency by feeding the chicks if food is less abundant.     

Inter-annual variation in the diet of female southern rockhopper penguin (Eudyptes chrysocome chrysocome) at Tierra del Fuego

Inter-annual variation in the diet of female southern rockhopper penguins (Eudyptes chrysocome chrysocome) at Staten Island was studied during the early chick-rearing period to investigate the components of the diet and highlight some points of the possible food web in the study area. Gregarious crustaceans, small juveniles of squid and octopus, fish larvae and juvenile fish dominated the diet. There was a high degree of variability in the relative contribution of the different prey taxa during the three seasons studied. Overall, crustaceans were by far the most abundant in terms of number. Cephalopods contributed less to numbers, while fish was the least represented of the prey item in 2 years. Inter-annual variation in the proportion of prey items consumed was apparent only for some prey species: Thysanoessa gregaria, Gonatus antarcticus, Themisto gaudichaudii, Harpagifer bispinis and Salilota australis. These data suggest variability in the prey resources at sea during the study period and a subsequent opportunism of this penguin species to exploit what is differentially available. In terms of the food web in the area, we suggest an apparent relationship in the availability between T. gaudichaudii and G. antarcticus, and between T. gaudichaudii and H bispinnis. These relationships emphasise the importance of understanding food web interactions, especially those involving multiple trophic levels, when determining the role of upper-trophic level predators in marine systems.     

The effect of investigators on the breeding success of royal,Eudyptes schlegeli,and rockhopper penguins,E. chrysocome,at Macquarie Island

The impact on reproductive success of investigators studying the breeding biology of royal and rockhopper penguins was assessed. Control and experimental transects were established in a colony of each species and the number of active nests, from egg laying to creche stage, were compared. Experimental nests were those used in breeding biology work, where birds were measured and banded, and nest checks were carried out at least once per week. Control nests were in equivalent locations but birds were not handled, and no contact was made with the nests once breeding had begun. There were no significant differences in the number of active nests between the control and experimental transects (and, therefore, breeding success) in either species. It is concluded that, provided care is taken when working with these species, no impacts on the short-term (up to creche stage, in one breeding season) breeding success of these populations will occur.     

The double vocal signature of crested penguins: is the identity coding system of rockhopper penguins Eudyptes chrysocome due to phylogeny or ecology?

Parent-offspring recognition systems are used in bird colonies to avoid misdirected parental care. In penguins, where the risk of confusion is particularly high, recognition is achieved by acoustic signals that constitute highly efficient vocal signatures. Comparisons between species from the Pygoscelis and Aptenodytes genera have revealed interspecific differences on the encoding of information within the signatures which correlate with the presence/absence of nests in the colonies. However a recent study of individual recognition in macaroni penguins Eudyptes chrysolophus revealed diversity within nest-building species. This paper investigates whether the original and intermediate signature system found in macaroni penguins is shared by another species of Eudyptes , the rockhopper penguin E. chrysocome . Vocal signatures of rockhopper penguins were analysed and compared to macaroni penguins'. We used a methodology derived from the theory of information to determine which parameters of the call were likely to encode individual identity. Playbacks of modified calls in the field complemented the analyses, and parent-chick reunions were compared between the two species. Our results reveal a similar double signature system within the Eudyptes genus, which integrates information simultaneously from the temporal and spectral domains. This double encoding is made through the tempo given by the successive syllables of the call and the harmonic content of the call. While it confirms the hypothesis that signatures are simpler in nest-building species, this result reveals differences in the efficacies of signatures within this category. This suggests that other parameters such as the mean distance recognition should be considered to account for the differences in the encoding of the vocal signatures and in their resulting efficacies.     

Diving patterns of breeding female rockhopper penguins (<Emphasis Type="Italic">Eudyptes chrysocome)</Emphasis>: Noir Island,Chile

The diving behaviour of female southern rockhopper penguins (Eudyptes chrysocome) was studied at Noir Island (54°30′S–73°00′W), Chile, in the southeast Pacific Ocean. This isolated island is located at the edge of the continental shelf in an area where the Humboldt Current originates, and holds a population of more than 150,000 breeding pairs. On 13 December 2005, four TDRs were successfully attached to females at the end of the brooding period and recorded diving activity at intervals of 2 s over the next 4 weeks. In total, 40 complete foraging trips were recorded. Trip duration was on average 42.4 ± 40.1 h and the proportion of overnight trips (60%) was the highest value found so far for this species. Mean dive depth and dive duration was 20.6 ± 19.4 m and 63.7 ± 36.4 s, respectively. The diving effort was higher than that of brooding females from the Indian Ocean and comparable with that of conspecifics from colonies in the southwest Atlantic in terms of diving rate (38 ± 14.2 dives h⁻¹), but slightly lower as regards the proportion of time spent underwater (61 ± 10.5%). This study confirms that the diving behaviour of rockhopper penguins varies as a function of the physical and biological characteristics of the foraging areas and of the particular stage of the breeding season.     

Inter-annual variation in provisioning behaviour of Southern Rockhopper Penguins Eudyptes chrysocome chrysocome at Staten Island, Argentina

Understanding the relationship between reproductive performance and food availability requires knowledge about many different variables, including such factors as the length of incubation shifts, provisioning rates and patterns, as well as how variability in these factors affects reproductive output. To examine some of the most important aspects of parental investment, we studied the provisioning behaviour and patterns of adult Southern Rockhopper Penguins Eudyptes chrysocome chrysocome breeding at Staten Island, Argentina. We investigated foraging trip duration, provisioning rates and chick survival using adult foraging patterns. Our results show that Rockhopper Penguins had clear sex-specific differences in their provisioning behaviour. Females provision chicks throughout chick rearing. By contrast, males provision chicks only during the crèche stage and at a slightly lower rate than females during this period. Foraging trips increased in length as the breeding season progressed. Rockhopper Penguins from Staten Island performed longer trips throughout the breeding season than do other species of Eudyptes at several other locations. Our results also show differences in parental investment between years that were related to differences in chick survival. We suggest that this was most likely to be related to female rather than male foraging behaviour as only females showed inter-annual differences in their provisioning rates.     

Genetic isolation and divergence in sexual traits: evidence for the northern rockhopper penguin Eudyptes moseleyi being a sibling species

The taxonomic status of populations of rockhopper penguins (Eudyptes chrysocome) is still enigmatic. Northern populations differ from southern ones in breeding phenology, song characteristics and head ornaments used as mating signals. We conducted a molecular analysis using mitochondrial DNA sequencing to test if there is a gene flow barrier between northern (subtropical) populations and southern (subantarctic) populations in relation to the Subtropical Convergence, a major ecological boundary for marine organisms. Sequences of the control region and the ND2 gene were analysed in rockhopper penguins and in the macaroni penguin (Eudyptes chrysolophus), a closely related species. Genetic distances and phylogenetic analyses showed a clear split into three clades, two rockhopper clades and the macaroni penguin. Moreover, Theta(ST) and gene flow estimates also suggested genetic structuring within the northern rockhoppers. Our results add further support to the notion that the two rockhopper penguin taxa, often considered as two subspecies, can be recognized as two species E. chrysocome and E. moseleyi. The divergence in mating signals found between these two taxa seems to have occurred recently and relatively rapidly. Thus, the behavioural changes may have been enough to isolate these taxa without the need for morphological differentiation. The findings have important conservational implications, since E. moseleyi is far less abundant than E. chrysocome, but more populations may warrant an uplisting to endangered status if full species status should be recognized for more subpopulations.     

Maternal deposition of yolk corticosterone in clutches of southern rockhopper penguins (Eudyptes chrysocome chrysocome)

High corticosterone levels can have deleterious effects in developing avian embryos and chicks. Therefore, it may be adaptive for avian mothers to reduce corticosterone transfer to their eggs. However, until now, data about the active or/and passive role of mothers in corticosterone transfer to eggs are inconclusive. Here, we study maternal investment into A- and B-eggs of southern rockhopper penguins (Eudyptes chrysocome chrysocome). This species exhibits reversed hatching asynchrony and provides a unique model to test whether there is a strategic investment in corticosterone favoring the B-chick, which is most likely to survive. We found that rockhopper penguins had the highest yolk concentrations of any wild bird species studied so far. Contrary to our expectations, B-eggs had more yolk corticosterone both in concentration and in quantity than A-eggs, independently of the laying period and the level of human disturbance. Additionally, females deposited more yolk corticosterone in their eggs when they were disturbed. However, this disturbance effect was particularly strong for A-eggs and for late-laid eggs. The present data support neither the predictions for an active regulation nor for a passive deposition, and hormone deposition mechanisms still need to be explored. The adaptive value, if any, of high yolk corticosterone is presently unknown.