Nocturnal predation of king penguins by giant petrels on the Crozet Islands

Dietary segregation of sympatric seabirds in the Southern Ocean is partly linked to differences in their foraging techniques. We have investigated the activity of giant petrels (Macronectes spp.) in a king penguin (Aptenodytes patagonicus) colony day and night during the austral winter of 2001 on the Crozet Islands. Using an automatic identification system and an infrared video camera, we followed 15 petrels tagged with micro transponders. Our data show that giant petrels predate king penguin chicks during the night. The activity of giant petrels is even slightly higher during nighttime than during the day. In addition, our data show a higher nocturnal activity by northern giant petrels (M. halli) than by southern giant petrels (M. giganteus). These unexpected results raise questions concerning visual adaptations to nocturnal foraging in giant petrels and their potential impact on the sleep, vigilance and crèching behavior of penguin chicks.     

A method to assess population changes in king penguins: the use of a Geographical Information System to estimate area-population relationships

During the last decades, king penguin (Aptenodytes patagonicus) populations have been reported to increase throughout most of their breeding range. In this study, we compared the results obtained from direct counts of incubating king penguins with the results yielded by the estimation of the change in area occupied by breeding birds at the Ratmanoff king penguin colony at the Kerguelen Islands. The area of the colony was determined using a Geographical Information System with a georeferencing extension on aerial pictures taken in 1963, 1985 and 1998. Individual king penguin were counted on the same pictures or pictures taken on the same day. The overall population increase between 1963 and 1998 was 733% while the colony area increased by 677%. This study indicates that monitoring change in colony size is a good indicator for detecting and monitoring large population changes in king penguins, in particular for remote colonies. The discrepancy between the two results may be from two different kinds of bias. Firstly, there could be a possible error in the estimation of the area occupied by the colony resulting from the georeferencing of oblique pictures, and secondly, the density of king penguins may also change with population number. This method, which only requires high-altitude pictures, also reduces the possible disturbance to breeding made by low- to medium-altitude flights. Accepted: 7 February 2000     

The endocrine basis of the reproductive cycle in the king penguin (Aptenodytes patagonicus)

What is the breeding frequency of the king penguin? More than 30 years of study and five major investigations, did not answer this question owing to the length (14 months) and the spreading (four months of laying) of reproductive events.
Following intensively during three consecutive years nearly 1000 tagged birds in a small colony, we obtained the individual history of a large part of the population. To these demographic and phenological studies, we have associated an endocrinological study validating blood samples and experiments in another colony.
The success or failure of a breeding cycle determines the timing of the subsequent breeding attempt. At Crozet Islands, the king penguin can rear one chick every two years at best: a successful breeding is followed by unsuccessful late breeding (or by non-breeding). So a large part of the population displays an annual periodicity of breeding attempts but with low individual breeding success.
The restarting of the reproductive cycle appears basically to be annual, the pituitary responding to the photoperiod. Steroid patterns present classical variations of level according to the reproductive stage. Prolactin (PRL) and luteinizing hormone (LH) are antagonists but, in this species, PRL remains high without external stimulation. To relay after failure in the field. we have experimentally to break down endogenous PRL. So, we have demonstrated that PRL has a key role in the reproductive cycle.
Paradoxically, the king penguin is an irregular breeder, quasi-biennial, although physiologically an annual breeder. In winter, there is not enough food at sea to rear the chick and during four months, the chick fasts. So a successful breeding cycle, which can be shortened to only nine months in captivity, is extended to more than a year for ecological reasons.     

Ticks Ixodes uriae and the breeding performance of a colonial seabird, king penguin Aptenodytes patagonicus

High densities of penguins in their colonies and the continuous use of these sites over consecutive reproductive periods increase the risk of development of tick populations. We have studied the effects of tick parasitism by Ixodes uriae in a colony of king penguins Aptenodytes patagonicus at Possession Island during three breeding seasons. We investigated the prevalence and periods of tick infestation during the one-year breeding cycle of penguins. The effects of tick parasitism on penguin breeding performance were assessed from photographs of the colony and with an automatic penguin identification system. We compared two groups of penguins carrying individual subcutaneous electronic tags, one group breeding in an infested area and the other in a non-infested area. Tick feeding activity was coincident with the periods when adult penguins stayed ashore for six days or more, i.e. during the incubating period. This duration corresponds to the duration of a tick meal on the host. The level of infestation varied between years. Penguins showed a lower incubating success in infested areas during a year of high infestation. In an infested area, individuals seen with ticks had a lower breeding success in rearing a one-year old chick than those seen without ticks.     

Acoustic communication in a king penguin colony: importance of bird location within the colony and of the body position of the listener

This study focuses on the propagation of the display call used for individual recognition between penguin partners. Transmission of acoustic information in a noisy environment such as a king penguin colony is very difficult. Conditions of propagation were examined for two areas of the colony (hatching and courtship areas) and reception at three heights from the ground (10, 45 and 90 cm). Signal modification was assessed in terms of attenuation of signal, amplitude modulation and spectral content. The acoustic recognition of the mate, which is decisive for breeding success, took place in the hatching area where signal degradation was less great for all parameters studied. When the receiver was located 10 cm above the ground, degradation of the signal was much more pronounced than when it was located 45 or 90 cm above ground. The characteristic incubating attitude of the king penguin (i.e. standing with the head at 45 cm above the ground) enables it to receive the main part of the signal in spite of the noisy environment. Accepted: 19 October 1998     

Factors affecting the breeding success of the south polar skua Catharacta maccormicki at Edmonson Point, Victoria Land, Antarctica

A south polar skua (Catharacta maccormicki) population was studied at Edmonson Point (74°20'S-165°08'E), Victoria Land, Antarctica, in 1998/1999. The local population consisted of 101 pairs, 89 of which were located within a large, loose colony associated with a rookery of about 2,000 pairs of Adélie penguin (Pygoscelis adeliae). Skua nests were clumped around penguin subcolonies. Mean skua Nearest Neighbour Distance (NND) was 21ᆣ m (n=89). NND was positively correlated with the distance from the nearest penguin subcolony. Mean laying date was 24Lj December (n=89). Mean clutch size was 1.9ǂ.2 eggs (n=89). Hatching success was 77% (n=174 eggs laid), and 20.2% of the breeding pairs successfully raised chicks to fledging. Mean number of fledged young was 0.2ǂ.4 per breeding pair (n=89), and 1 per successful pair (n=18). Main causes of breeding failure were intraspecific predation and sibling aggression. Breeding success was negatively related to distance from the nearest penguin nest and to laying date. Because of the extensive and persistent sea-ice cover, penguins represented an important source of food for the skua population.     

Assessing the impact of extreme adverse weather on the biological traits of a European storm petrel colony

Climate change affects the climatic disturbance patterns and regimes and is altering the frequency and intensity of subtropical cyclones. These events can affect population dynamics of seabirds (e.g., survival, reproduction). In this work we tested the effect of adverse weather on a colony of European storm petrels (Hydrobates pelagicus) located in a small islet (Aketx) in northern Spain. Over a long-term monitoring period (1993–2014) we ringed 3728 petrels. From 2003 onwards we also monitored breeding success, the percentage of immature individuals and moult scores. We used Cormack-Jolly-Seber models and Underhill and Zucchini models to analyze the effects of climatic conditions on a number of biological traits (survival, breeding parameters, moulting patterns). Our analyses revealed a constant value of adult survival over the 26-year monitoring period. Recapture probability, however, tended to be positively influenced by NAO conditions in spring, and negatively influenced by NAO conditions in winter (although this would only affect to a fraction of first-captured birds). Moreover, the impact of adverse weather, especially in 2011 and 2014, resulted in an increasing proportion of yearlings in the breeding population, a lower breeding success and a delayed onset of moult. These effects were similar to those observed during the Prestige oil spill catastrophe.     

Is Penguin banding harmless?

Thousands of penguins are banded annually world-wide, even though little is known about the potential impact of these flipper bands. In this paper, the possible effect of banding on the survivorship, breeding frequency and other ecological factors on king penguins was investigated. The extended laying period (3–4 months) of the king penguin allows the observation of non-lethal effects that could influence the time of laying and thus the reproductive success. Three hundred and eighty-three breeding king penguins on the colony of “la Baie du Marin” on Possession Island, Crozet Archipelago were either single- or double-flipper banded. The results show that the returning birds were laying late the following breeding season, and that double-banded birds lay significantly later than single-banded birds. Furthermore, our data suggest a lower return rate for double-banded birds than for single-banded birds (45% as opposed to 76%). The low return rate of single-banded birds, when compared to an interannual survivorship estimated to be 96.5%, also raises questions concerning the potential impact of single banding. Received: 2 January 1998 / Accepted: 23 May 1998     

Population trends and reproductive success at a frequently visited penguin colony on the western Antarctic Peninsula

Petermann Island (65°10′S, 64°10′W), one of the Antarctic Peninsula’s most frequently visited locations, is at the epicenter of a rapid shift in which an Adélie penguin dominated fauna is becoming gentoo penguin dominated. Over the course of five seasons, the breeding productivity of Adélie and gentoo penguins breeding at Petermann Island were monitored to identify drivers of this rapid community change. The impact of tourist visitation on breeding success was also investigated. Consistent with larger trends in this region, the Adélie penguin population decreased by 29% and the gentoo penguin population increased by 27% between the 2003/2004 and 2007/2008 seasons. Reproductive success among Adélie penguins ranged from 1.09 to 1.32 crèched chicks/nest, which was higher than or comparable to other sites and is an unlikely explanation for the precipitous decline of Adélie penguins at Petermann Island. Whereas gentoo penguin reproductive success was lowest in colonies frequently visited by tourists, Adélie penguin colonies frequently visited by tourists had higher reproductive success than those visited only occasionally. These results are placed in the context of other studies on reproductive success and the impact of tourist visitation on breeding colonies of Adélie and gentoo penguins.     

Predation risk and moonlight avoidance in nocturnal seabirds

Unlike most seabird families, the vast majority of small petrel species are nocturnal on their breeding grounds. Further, they reduce markedly their activity when the light level increases. Moonlight avoidance might be a consequence of reduction in foraging profitability, as bioluminescent prey do not come to the sea surface on bright nights. Alternatively, petrels may avoid colonies during moonlit nights because of increased predation risk. We studied predation on petrels by Brown Skuas Catharacta antarctica lönnbergi at Kerguelen, and the influence of moonlight on behaviour of both skuas and petrels, to test the 'predation risk' hypothesis. On the study area, Brown Skuas hunt at night and prey heavily upon the Blue Petrel Halobaena caerulea and the Thin-billed Prion Pachyptila belcheri . Predation risk was higher on moonlit nights, as skuas caught more prey, and particularly more Blue Petrels when the light level increased. Nightly intakes of Blue Petrel and Thin-billed Prion by skuas was related to colony attendance of non-breeders rather than that of breeders. Biometry of prey also suggested that skuas caught a higher proportion of non-breeding birds than was present at the colonies. Predation risk was thus greater in non-breeders and on moonlit nights. Colony attendance by non-breeding Blue Petrels and Thin-billed Prions was also reduced during moonlit nights. Vocal activity, which is mainly by non-breeders, was also drastically reduced when the light level increased in the species suffering the highest predation rate. Our results supported the 'predation risk' hypothesis, although the 'foraging efficiency' and the 'predation risk' hypotheses are not mutually exclusive: the former might explain the moonlight avoidance behaviour of breeding, and the latter that of non-breeding individuals.     

Long-term population trends in seven Antarctic seabirds at Pointe Géologie (Terre Adélie) Human impact compared with environmental change

Antarctic seabird populations have been much studied over the last decades as bioindicators of the nature of variability in the Southern Ocean marine ecosystem, and most attention has been focused on the role of food supply and the extent of sea ice. In addition, the rapid spread of tourism and the activities of researchers since the early 1960s have raised questions related to their real and potential impact on bird populations. Our data sets start in 1952 for several species of Antarctic seabirds and this study documents the trends over a 14-year period (1985–1999) in seven species breeding on Pointe Géologie archipelago (Terre Adélie, Antarctica). This is the first study where the direct impact of destruction of breeding sites (for building of an airstrip) is examined and where such long-term populations trends have been assessed in such a number of Antarctic species at one site. Trends from 1985 show that for the whole archipelago and when excluding islands destroyed, Adélie penguins and south polar skuas were the only species to show a significant increase (>3.5% annual change). The others species showed opposite trends, three increasing slightly (southern fulmars +0.4%, cape petrels +2.3%, snow petrels +0.9%) and two decreasing (emperor penguin −0.9%, southern giant petrel −3.9%). Three species particularly affected by the destruction of their breeding habitat (Adélie penguin, cape petrel, snow petrel) showed the capability to restore their populations. The availability of food and nesting sites is discussed in relation to environmental change. Species feeding on krill (Adélie penguins and cape petrels) increased more than other species; however, decrease of ice cover can increase availability of nesting sites. The importance of long-term studies is shown when assessing the role of human activities in Antarctica compared to larger-scale changes. Accepted: 18 September 2000     

Spatial Heterogeneity as a Genetic Mixing Mechanism in Highly Philopatric Colonial Seabirds

How genetic diversity is maintained in philopatric colonial systems remains unclear, and understanding the dynamic balance of philopatry and dispersal at all spatial scales is essential to the study of the evolution of coloniality. In the King penguin, Aptenodytes patagonicus, return rates of post-fledging chicks to their natal sub-colony are remarkably high. Empirical studies have shown that adults return year after year to their previous breeding territories within a radius of a few meters. Yet, little reliable data are available on intra- and inter-colonial dispersal in this species. Here, we present the first fine-scale study of the genetic structure in a king penguin colony in the Crozet Archipelago. Samples were collected from individual chicks and analysed at 8 microsatellite loci. Precise geolocation data of hatching sites and selective pressures associated with habitat features were recorded for all sampling locations. We found that despite strong natal and breeding site fidelity, king penguins retain a high degree of panmixia and genetic diversity. Yet, genetic structure appears markedly heterogeneous across the colony, with higher-than-expected inbreeding levels, and local inbreeding and relatedness hotspots that overlap predicted higher-quality nesting locations. This points towards heterogeneous population structure at the sub-colony level, in which fine-scale environmental features drive local philopatric behaviour, while lower-quality patches may act as genetic mixing mechanisms at the colony level. These findings show how a lack of global genetic structuring can emerge from small-scale heterogeneity in ecological parameters, as opposed to the classical model of homogeneous dispersal. Our results also emphasize the importance of sampling design for estimation of population parameters in colonial seabirds, as at high spatial resolution, basic genetic features are shown to be location-dependent. Finally, this study stresses the importance of understanding intra-colonial dispersal and genetic mixing mechanisms in order to better estimate species-wide gene flows and population dynamics.     

Annual variation in breeding biology of gentoo penguins, Pygoscelis papua, at Bird Island, South Georgia

The breeding biology of the gentoo penguin, Pygoscelis papua , was studied over a three-year period (1986–1988) at Bird Island, South Georgia, with particular reference to birds of known age or breeding experience. Laying date varied significantly between all three years, being three weeks later in 1987, when the breeding population decreased markedly. Factors involved in the timing of breeding are discussed. Within years egg-laying was highly synchronous: 95% of clutches were initiated in 14·5 days or less. The incubation period was 35 days and the laying interval, between the two eggs, 3·3–3·4 days. Chicks creched when 25–30 days old, and this varied between years, possibly related to food supply and chick growth. Chicks left the colony for the first time between 75 and 85 days of age. The breeding population at Bird Island decreased by 20% and increased by 84% in successive years during the study period. Breeding success (chicks fledged per egg laid) varied between 0·33 and 0·65 within colonies, but for the whole island was very consistent over the three years: 0·45, 0·51 and 0·47. Overall, colony differences were not correlated between years. Disturbance from Antarctic fur seals, Arctocephalus gazella , is suggested as the cause of consistently lower breeding success at one colony. Mean egg weight varied annually, and with age of the breeding bird, nest location and, in one year, with laying date. Young, first-time breeders laid smaller eggs and had lower breeding success compared to older, experienced birds, similar to other seabirds. However, they differed from other species in laying on average earlier than older birds. The relationship between age, egg weight, laying date and breeding success is discussed in relation to predation and seasonal food supply.     

Predation by cats could lead to the extinction of the Mediterranean endemic Yelkouan Shearwater Puffinus yelkouan at a major breeding site

Feral cats are considered to be one of the main harmful invasive species for island species. Adult shearwaters are highly vulnerable to predation by cats. The population of the Yelkouan Shearwater Puffinus yelkouan, a species endemic to the Mediterranean, is predicted to decline, leaving only a few large breeding colonies, due to the invasion of cats. The impact of cats on the Shearwater population of Le Levant Island, one of the major breeding sites for this species, was evaluated by studying cat diet over a 2‐year period. The predation rate obtained was then included in a Shearwater demographic model. Cats preyed upon rabbits, rats and Shearwaters, with a peak of predation on Shearwaters immediately upon their arrival at the colony. Cat predation was heavy and responsible for the yearly death of about 810–3241 birds. This could lead to the extinction of the Le Levant colony within the next four decades and perhaps within just a few years. Cat predation on prospecting individuals, a parameter essential to assess the real impact of predation, may not have an immediate effect on the Shearwater breeding population but can accelerate population extinction. Cat predation must be reduced or removed to prevent the extinction of one of the most important breeding sites for this species.     

Can thin-billed prions <Emphasis Type="Italic">Pachyptila belcheri</Emphasis> breed successfully on an island with introduced rats,mice and cats? The case of New Island,Falkland Islands

Small burrowing petrels nesting on islands rarely survive introductions of mammalian predators. On New Island, a population of around two million pairs of thin-billed prions nests despite the presence of introduced ship rats, house mice and feral cats. Understanding the mechanisms of such coexistence is important, as it is important to establish a baseline for future monitoring. To do this, prion breeding success was determined for 7 years and in several habitats. Breeding success was high, except for the small fraction of the population that nests in tussock Poa flabellata stands, where several lines of evidence suggest significant predation by rats. Such high breeding success possibly resulted from predator swamping in this highly seasonal environment. This study suggests that introduced mammals do not currently depress thin-billed prion breeding success on New Island. However, cats and rodents might have future harmful effects if external factors depressed the prion population or allow a significant population growth of predators on New Island.     

First direct, site-wide penguin survey at Deception Island, Antarctica, suggests significant declines in breeding chinstrap penguins

Deception Island (62°57′S, 60°38′W) is one of the most frequently visited locations in Antarctica, prompting speculation that tourism may have a negative impact on the island’s breeding chinstrap penguins (Pygoscelis antarctica). Discussions regarding appropriate management of Deception Island and its largest penguin colony at Baily Head have thus far operated in the absence of concrete information regarding the current size of the penguin population at Deception Island or long-term changes in abundance. In the first ever field census of individual penguin nests at Deception Island (December 2–14, 2011), we find 79,849 breeding pairs of chinstrap penguins, including 50,408 breeding pairs at Baily Head and 19,177 breeding pairs at Vapour Col. Our field census, combined with a simulation designed to capture uncertainty in an earlier population estimate by Shuford and Spear (Br Antarct Surv Bull 81:19–30, 1988), suggests a significant (>50?%) decline in the abundance of chinstraps breeding at Baily Head since 1986/1987. A comparative analysis of high-resolution satellite imagery for the 2002/2003 and the 2009/2010 seasons suggests a 39?% (95th percentile CI?=?6–71?%) decline (from 85,473?±?23,352 to 52,372?±?14,309 breeding pairs) over that 7-year period and provides independent confirmation of population decline in the abundance of breeding chinstrap penguins at Baily Head. The decline in chinstrap penguins at Baily Head is consistent with declines in this species throughout the region, including sites that receive little or no tourism; as a consequence of regional environmental changes that currently represent the dominant influence on penguin dynamics, we cannot ascribe any direct link between chinstrap declines and tourism from this study.     

Shape can influence the rate of colony fragmentation in ground nesting seabirds

There have been catastrophic population declines at a number of rockhopper penguin Eudyptes chrysocome rookeries over the past 50 years or so. At Campbell Island, New Zealand, large contiguous rookeries have fragmented into much smaller subcolonies and although the underlying cause of the major part decline was possibly diet related, it seems likely that predation may be having an increasingly important impact. In an extension of selfish herd ideas, we hypothesised that since predation and colony contraction are edge related, the initial shape of the colony may play an important role in how quickly it might fragment and in turn how long it might persist. Intuition tells us that fragmentation is likely to occur on these smaller subcolonies and that their shape will likely affect their rate of fragmentation. We provide the first quantitative assessment of this qualitative theory of fragmentation risk as a function of colony shape for a range of hypothetical colonies.     

Predator‐avoidance behaviour in a nocturnal petrel exposed to a novel predator

Many species of bird recognize acoustic and visual cues given by their predators and have complex defence adaptations to reduce predation risk. Recognition of threats posed by specific predators and specialized anti‐predation behaviours are common. In this study we investigated predator recognition and anti‐predation behaviours in a pelagic seabird, Leach's Storm‐petrel Oceanodroma leucorhoa, at a site where predation risk from Great Skuas Stercorarius skua is exceptionally high. Leach's Storm‐petrels breed in burrows and come on land only at night. Counter‐predator adaptations were investigated correlatively in relation to changing natural light levels at night, and experimentally in relation to nocturnal visual and acoustic signals from Great Skuas. Colony attendance by Leach's Storm‐petrels was attuned to changes in light conditions at night and was highest when nights were darkest. This behaviour is likely to reduce predation risk on land; however, specific recognition of Great Skuas and specialized defence behaviours were not found. Leach's Storm‐petrels, in particular apparently non‐breeding individuals, were entirely naïve to the threat posed by Great Skuas and were captured easily in a variety of different ways, on the ground and in the air. Lack of specialized behavioural adaptations in Leach's Storm‐petrels against Great Skuas may be because spatial overlap of breeding distributions of these species appears to be a rare and recent phenomenon.     

Feeding territoriality and the reproductive consequences in brown skuas<Emphasis Type="Italic"> Catharacta antarctica lonnbergi</Emphasis>

In the maritime Antarctic, brown skuas (Catharacta antarctica lonnbergi) show two foraging strategies: some pairs occupy feeding territories in penguin colonies, while others can only feed in unoccupied areas of a penguin colony without defending a feeding territory. One-third of the studied breeding skua population in the South Shetlands occupied territories of varying size (48 to >3,000 penguin nests) and monopolised 93% of all penguin nests in sub-colonies. Skuas without feeding territories foraged in only 7% of penguin sub-colonies and in part of the main colony. Females owning feeding territories were larger in body size than females without feeding territories; no differences in size were found in males. Territory holders permanently controlled their resources but defence power diminished towards the end of the reproductive season. Territory ownership guaranteed sufficient food supply and led to a 5.5 days earlier egg-laying and chick-hatching. Short distances between nest and foraging site allowed territorial pairs a higher nest-attendance rate such that their chicks survived better (71%) than chicks from skua pairs without feeding territories (45%). Due to lower hatching success in territorial pairs, no difference in breeding success of pairs with and without feeding territories was found in 3 years. We conclude that skuas owning feeding territories in penguin colonies benefit from the predictable and stable food resource by an earlier termination of the annual breeding cycle and higher offspring survivorship.Research licence: Umweltbundesamt Bonn 13.4-94003-1/5-7.     

King penguin population on Macquarie Island recovers ancient DNA diversity after heavy exploitation in historic times

Historically, king penguin populations on Macquarie Island have suffered greatly from human exploitation. Two large colonies on the island were drastically reduced to a single small colony as a result of harvesting for the blubber oil industry. However, recent conservation efforts have resulted in the king penguin population expanding in numbers and range to recolonize previous as well as new sites. Ancient DNA methods were used to estimate past genetic diversity and combined with studies of modern populations, we are now able to compare past levels of variation with extant populations on northern Macquarie Island. The ancient and modern populations are closely related and show a similar level of genetic diversity. These results suggest that the king penguin population has recovered past genetic diversity in just 80 years owing to conservation efforts, despite having seen the brink of extinction.