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.     

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.     

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     

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.     

Maximum diving depths of northern rockhopper penguins (Eudyptes chrysocome moseleyi) at Amsterdam Island

 The mean maximum dive depth from 49 foraging bouts by northern rockhopper penguins, measured using capillary-tube depth gauges, was 66±4 m (12–168 m). There were no differences in the maximum dive depths between male and female penguins. Northern rockhopper penguins dived deeper in early than in late creche stages (83±7 vs 57±4 m), and this was associated with probable dietary changes, squid dominating the diet by mass (44%) in November, and fish (64%) in December 1994 at Amsterdam Island. Received: 10 January 1996/Accepted: 31 March 1996     

Population trends, breeding success and diet composition of gentoo Pygoscelis papua, magellanic Spheniscus magellanicus and rockhopper Eudyptes chrysocome penguins in the Falkland Islands. A review

Data on population size, breeding success and diet composition of gentoo (Pygoscelis papua), magellanic (Spheniscus magellanicus) and rockhopper (Eudyptes chrysocome) penguins, collected as part of the Falkland Island Seabird Monitoring Programme from 1986/1987 to 1998/1999, were analysed with regard to spatial and temporal variation, as well as potential interaction with local commercial fisheries. No significant population trends were detectable, mainly because of the short time-series and large spatial and inter-annual variation in the number of breeding pairs in the colonies monitored. However, the breeding success of all three penguin species has improved slightly over the last few years, indicating a potential for increasing populations in the near future. During the breeding season, all three penguin species preyed opportunistically on a mixture of fish, squid and crustaceans. Diet composition too showed a high degree of spatial and temporal variation. However, in all three penguin species studied, squid gradually disappeared from the diet over successive years, to be replaced by fish. Coincidentally, the commercial catches of the squid species Loligo gahi in Falkland Islands waters decreased and the by-catch of nototheniid fish increased. All three penguin species compete directly with the commercial fishing fleet for L. gahi; however, there may also be competition for Patagonian toothfish (Dissostichus eleginoides), hake (Merluccius sp.) and southern blue whiting (Micromesistius australis), because juveniles of these species were found regularly in penguin diets.     

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.     

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.     

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.     

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.     

Increasing trend in the number of Southern Rockhopper Penguins (Eudyptes c. chrysocome) breeding at the Falkland Islands

The Falkland Islands currently supports one of the largest Southern Rockhopper Penguin (Eudyptes c. chrysocome) populations. Archipelago-wide censuses conducted in 2000 and 2005 revealed that the number of breeding pairs had declined by 30 % during this period. To establish whether the breeding population continued to decline, an archipelago-wide census was conducted in 2010. We report a conservative estimate of 319,163 ±SD 24,820 pairs breeding at the Falkland Islands in 2010. This represents a 51 % increase when compared with the number counted in 2005. A simple stochastic population model was developed to investigate the extent to which changes in demographic parameters between 2005 and 2010 could account for the increase in breeding pairs. The population model predicted a 38 % increase in the number of breeding pairs over a 5-year period (289,431 ±SD 24,615). The increase in the number of breeding pairs was therefore probably attributed to improved vital rates in the period between the 2005 and 2010 archipelago-wide censuses in combination with other factors such as a reduction in the proportion of adult birds that abstained from breeding. Based on the 2010 Falkland Islands estimate, the global population of the subspecies E. c. chrysocome is now closer to 870,000 breeding pairs of which the Falkland Islands accounts for approximately 36 %, the second largest proportion after Chile. We conclude that despite fluctuations, the number of Southern Rockhopper Penguins breeding at the Falkland Islands has increased over the last 15 years and suggest that the ‘Vulnerable’ conservation status of the species be re-assessed.     

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.     

Temporal variation in the diet of gentoo penguins at the Falkland Islands

Knowledge of diet is critical in interpreting the ecological roles of marine top predators and provides information towards their conservation and management. The Falkland Islands hold the largest number of breeding gentoo penguins. Yet knowledge of gentoo penguin diet at the Falklands is limited to either broad taxonomic divisions of prey items or dietary samples collected only on a single day. This study is the first to investigate gentoo penguin diet at Cow Bay, Falklands, to the species level, over repeated sampling intervals during the breeding period. Through stomach content analysis, we determined diet over a large temporal scale (2002/2003/2004–2011/2012/2013) and between the guard and crèche periods of chick rearing. The principle prey item by reconstituted mass was rock cod fish Patagonotothen spp., for all periods (47–78 %) except that of the 2012/2013 crèche period (19 %) when Falkland herring Sprattus fugensis made up the bulk of the diet (52 %). Of the cephalopods recovered, Patagonian squid Doryteuthis gahi was prominent (1–24 %), while crustaceans contributed negligibly to gentoo penguin diet. Our findings revealed that gentoo penguins breeding at the Falkland Islands were primarily demersal foragers with an ability for pelagic feeding. Diet choice appears to reflect prey availability.     

A stable isotopic investigation into the causes of decline in a sub-Antarctic predator, the rockhopper penguin Eudyptes chrysocome

The rockhopper penguin (Eudyptes chrysocome) is a conspicuous apex marine predator that has experienced marked population declines throughout most of its circumpolar breeding distribution. The cause(s) for the declines remain elusive, but the relatively large spatio‐temporal scale over which population decreases have occurred implies that ecosystem‐scale, at‐sea factors are likely to be involved. We employ stable isotope analyses of carbon (¹³C/¹²C, expressed as δ¹³C) and nitrogen (¹⁵N/¹⁴N, δ¹⁵N) in time‐series of rockhopper penguin feather samples, dating back to 1861, in order to reconstruct the species' ecological history. Specifically, we examine whether rockhopper penguin population decline has been associated with a shift towards lower primary productivity in the ecosystem in which they feed, or with a shift to a diet of lower trophic status and lower quality, and we use long‐term temperature records to evaluate whether shifts in isotope ratios are associated with annual variations in sea surface temperature. Having controlled temporally for the Suess Effect and for increases in CO₂ concentrations in seawater, we found that overall, δ¹³C signatures decreased significantly over time in rockhopper penguins from seven breeding sites, supporting the hypothesis that decreases in primary productivity, and hence, carrying capacity, for which δ¹³C signature is a proxy, have been associated with the decline of penguin populations. There was some evidence of a long‐term decline in δ¹⁵N at some sites, and strong evidence that δ¹⁵N signatures were negatively related to sea surface temperatures across sites, indicative of a shift in diet to prey of lower trophic status over time and in warm years. However, a site‐by‐site analysis revealed divergent isotopic trends among sites: five of seven sites exhibited significant temporal or temperature‐related trends in isotope signatures. This study highlights the utility of stable isotope analyses when applied over relatively long timescales to apex predators.     

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.     

Satellite tracking of the winter migration of Magellanic Penguins Spheniscus magellanicus breeding in the Falkland Islands

Magellanic penguin populations in the Falkland Islands may have decreased over the past decade. The post-breeding migration may be the period in which the birds are most vulnerable. To investigate this we equipped ten Magellanic Penguins after their moult at Seal Bay (51̀38'S, 58̀03'W), East Falkland, with satellite transmitters. The movements of the penguins were tracked for between 15 and 99 days until transmission ceased. All birds initially migrated to the northwest. However, four birds entered Argentinean coastal waters, then headed northeast following the coastline, The other penguins remained offshore, but also changed to a northeasterly course. Two birds migrated beyond 36̀S with a maximum distance to the colony of more than 1800 km, while the minimum distance travelled was up to 2700 km. Initially, the birds migrated quickly but their speed was reduced and became more variable as time progressed. A high concentration of positional fixes, associated with low travelling speeds, indicated at least four different areas where birds were assumed to forage efficiently. The relevance of these areas is discussed with respect to the diet of Magellanic Penguins and possible interactions with human activities.