Satellite remote sensing in monitoring change of seabirds: use of Spot Image in king penguin population increase at Ile aux Cochons,Crozet Archipelago

The king penguin colony at Ile aux Cochons, Crozet Archipelago (southern Indian Ocean) is the largest in the world. The change in its surface area was investigated by means of satellite remote sensing using spot scene. The satellite picture enabled us to locate the colony and to determine that the surface area occupied by the colony has increased by 56% between 1962 and 1988. The increase in the surface area occupied by the colony was confirmed by a map realised in 1982 (by the Institut Géographique National). The high resolution system available on the spot system which allows at present at 10 m ground resolution, and 5 m in the near future, can thus be a useful tool for monitoring medium to long-term changes in marine bird populations breeding in colonies composed of birds spaced a constant distance from one another. Based on the surface area occupied by the colony and the published data on the population size on Possession Island, as well as information on the breeding frequency of the species, we estimated that the total breeding population is about 1,000,000 pairs for the whole archipelago and that about 70% of birds breed at Ile aux Cochons.     

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.     

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     

Impact of predation on king penguin Aptenodytes patagonicus in Crozet Archipelago

Predation can have major effects on population dynamics, but predator–prey interactions in marine ecosystems have rarely been studied. While the king penguin is one of the most studied seabirds, little is known about the impact of predation on its population dynamics. Here, we determine the impact of the main predators (giant petrels and skuas) on king penguin breeding success taking into account the nocturnal predation of petrels. We found that predation is the most important source of breeding failure for king penguins. The smallest chicks within crèches are the most hunted. The periphery of the colony suffers the highest risk of predation during summer. Our study shows the unequal quality of some areas inside the colony in terms of predation risk and breeding success, and points out the importance of timing in successful breeding.     

Growth and decline of a penguin colony and the influence on nesting density and reproductive success

Colonial breeding is characteristic of seabirds but nesting at high density has both advantages and disadvantages and may reduce survival and fecundity. African penguins (Spheniscus demersus) initiated breeding at Robben Island, South Africa in 1983. The breeding population on the island increased in the late 1990s and early 2000s before decreasing rapidly until 2010. Before the number breeding peaked, local nest density in the areas where the colony was initiated plateaued, suggesting that preferred nests sites were mostly occupied, and the area used by breeding birds expanded. However, it did not contract again as the population decreased, so that nesting density varied substantially. Breeding success was related positively to the prey available to the breeding birds and negatively to local nest density, particularly during the chick-rearing period, suggesting a density-dependence operating through social interactions in the colony, possibly exacerbated by poor prey availability when the breeding population was large. Although nest density at Robben Island was not high, nesting burrows, which probably reduce the incidence of aggressive encounters in the colony, are scarce and our results suggest that habitat alteration has modified the strength of density-dependent relationships for African penguins. Gaining a better understanding of how density dependence affects fecundity and population growth rates in colonial breeders is important for informing conservation management of the African penguin and other threatened taxa.     

An emperor penguin population estimate: the first global, synoptic survey of a species from space

Our aim was to estimate the population of emperor penguins (Aptenodytes fosteri) using a single synoptic survey. We examined the whole continental coastline of Antarctica using a combination of medium resolution and Very High Resolution (VHR) satellite imagery to identify emperor penguin colony locations. Where colonies were identified, VHR imagery was obtained in the 2009 breeding season. The remotely-sensed images were then analysed using a supervised classification method to separate penguins from snow, shadow and guano. Actual counts of penguins from eleven ground truthing sites were used to convert these classified areas into numbers of penguins using a robust regression algorithm.We found four new colonies and confirmed the location of three previously suspected sites giving a total number of emperor penguin breeding colonies of 46. We estimated the breeding population of emperor penguins at each colony during 2009 and provide a population estimate of ~238,000 breeding pairs (compared with the last previously published count of 135,000-175,000 pairs). Based on published values of the relationship between breeders and non-breeders, this translates to a total population of ~595,000 adult birds.There is a growing consensus in the literature that global and regional emperor penguin populations will be affected by changing climate, a driver thought to be critical to their future survival. However, a complete understanding is severely limited by the lack of detailed knowledge about much of their ecology, and importantly a poor understanding of their total breeding population. To address the second of these issues, our work now provides a comprehensive estimate of the total breeding population that can be used in future population models and will provide a baseline for long-term research.     

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.     

Projected poleward shift of king penguins' (Aptenodytes patagonicus) foraging range at the Crozet Islands, southern Indian Ocean

Seabird populations of the Southern Ocean have been responding to climate change for the last three decades and demographic models suggest that projected warming will cause dramatic population changes over the next century. Shift in species distribution is likely to be one of the major possible adaptations to changing environmental conditions. Habitat models based on a unique long-term tracking dataset of king penguin (Aptenodytes patagonicus) breeding on the Crozet Islands (southern Indian Ocean) revealed that despite a significant influence of primary productivity and mesoscale activity, sea surface temperature consistently drove penguins' foraging distribution. According to climate models of the Intergovernmental Panel on Climate Change (IPCC), the projected warming of surface waters would lead to a gradual southward shift of the more profitable foraging zones, ranging from 25 km per decade for the B1 IPCC scenario to 40 km per decade for the A1B and A2 scenarios. As a consequence, distances travelled by incubating and brooding birds to reach optimal foraging zones associated with the polar front would double by 2100. Such a shift is far beyond the usual foraging range of king penguins breeding and would negatively affect the Crozet population on the long term, unless penguins develop alternative foraging strategies.     

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.     

Responses of king penguin Aptenodytes patagonicus adults and chicks to two food‐related odours

Increasing evidence suggests that penguins are sensitive to dimethyl sulphide (DMS), a scented airborne compound that a variety of marine animals use to find productive areas of the ocean where prey is likely to be found. Here we present data showing that king penguins Aptenodytes patagonicus are also sensitive to DMS. We deployed DMS on a lake near a king penguin colony at Ratmanoff beach in the Kerguelen archipelago. We also presented DMS to ‘sleeping’ adults on the beach. On the lake, penguins responded to the DMS deployments by swimming more, while on the beach, penguins twitched their heads and woke up more for the DMS than for the control presentations. Interestingly, penguins did not respond to cod liver oil deployments on the lake; mirroring at‐sea studies of other penguins. Although at‐sea studies are needed to confirm that king penguins use DMS as a surface cue that informs them of productivity under the water, this study is an important first step in understanding how these birds locate prey over significant distances.     

Stomach stones in king penguin chicks

Many animals that possess a gizzard swallow stones or sandy grit, supposedly to aid in the mechanical breakdown of food. While this has been well documented in the literature, our study is the first to report the presence of stones in the gizzard of king penguin chicks. We found stones, so called ‘gastroliths’, in the pyloric region of the gizzard, the part of the digestive tract that is specialised for the mechanical breakdown of food. Stones were already present in the gizzard of chicks and, hence, during the first year of the life of king penguins, which is spent on land. Some chicks were found to have more than 130 stones (0.5–22 mm in size) in their gizzard. The gastroliths we found in king penguins are of the same geological origin as rocks present at the colony, which suggests that birds swallowed them there. The functional role of gastroliths in penguin chicks and adults is still unknown. We discuss the potential roles that these gastroliths might play in king penguins (i.e. aid in digestion, buoyancy control during foraging at sea, adaptation to fasting).     

The winter migration of Adelie penguins breeding in the Ross Sea sector of Antarctica

Satellite telemetry was used to monitor the migratory movements of a single Adelie penguin (Pygoscelis adeliae) from Cape Hallett (72.31°S, 170.21°E) following the 1997/1998 breeding season. Locations were obtained using the ARGOS satellite system and compared with the migratory paths taken by two penguins from the Northern Colony at Cape Bird, Ross Island (77.22°S, 166.48°E) following the 1990/1991 breeding season. Although the sample sizes are small, if representative they would indicate that: (1) Adelie penguins breeding in the Ross Sea follow a common migratory path, (2) Adelie penguins breeding in the Ross Sea may travel to a common over-winter feeding ground west and north of the Balleny Islands, and (3) Adelie penguins breeding at 77°S on Ross Island travel nearly twice the distance during their over-winter migration as do those penguins breeding at Cape Hallett and colonies further north. While the Cape Hallett penguin was tracked successfully for 172 days, a record for Adelie penguins, the problem of long-term attachment of transmitters to penguins remains.     

The challenges of detecting subtle population structure and its importance for the conservation of emperor penguins

Understanding the boundaries of breeding populations is of great importance for conservation efforts and estimates of extinction risk for threatened species. However, determining these boundaries can be difficult when population structure is subtle. Emperor penguins are highly reliant on sea ice, and some populations may be in jeopardy as climate change alters sea‐ice extent and quality. An understanding of emperor penguin population structure is therefore urgently needed. Two previous studies have differed in their conclusions, particularly whether the Ross Sea, a major stronghold for the species, is isolated or not. We assessed emperor penguin population structure using 4,596 genome‐wide single nucleotide polymorphisms (SNPs), characterized in 110 individuals (10–16 per colony) from eight colonies around Antarctica. In contrast to a previous conclusion that emperor penguins are panmictic around the entire continent, we find that emperor penguins comprise at least four metapopulations, and that the Ross Sea is clearly a distinct metapopulation. Using larger sample sizes and a thorough assessment of the limitations of different analytical methods, we have shown that population structure within emperor penguins does exist and argue that its recognition is vital for the effective conservation of the species. We discuss the many difficulties that molecular ecologists and managers face in the detection and interpretation of subtle population structure using large SNP data sets, and argue that subtle structure should be taken into account when determining management strategies for threatened species, until accurate estimates of demographic connectivity among populations can be made.     

Modeling the marine resources consumed in raising a king penguin chick: an energetics approach

Accurate estimates of penguin energetics would represent an important contribution to our understanding of the trophodynamics of the Southern Ocean ecosystem and our ability to predict effects of environmental change on these species. We used the heart rate-rate of oxygen consumption technique to estimate rate of energy expenditure in adult king penguins raising a chick, in combination with data from the literature on changes in adult mass, chick energy requirements, and prey energy density. Our model estimated a variety of energetic costs and quantities of prey consumption related to raising a king penguin chick during the austral summer. The total energy requirements of a king penguin chick at the Crozet Archipelago from hatching until reaching a mass of 8 kg 90 d later is 271 MJ, representing the consumption of 38.4 kg of myctophid fish. A successfully breeding male requires 0.78 kg d(-1) of fish during the entirety of the incubation period and 1.14 kg d(-1) during the subsequent 90 d of chick rearing. Assuming the same energy requirements for females, the estimated 580,000 pairs of king penguins that breed successfully at Crozet each year, together with their chicks, consume a total of around 190,000 tons of fish during the incubation and summer rearing periods combined. If, due to depletion of fish stocks, the diet of breeders and chicks during the summer becomes identical to the typical diet of adults during the austral winter, the mass of prey required by both adults and chicks combined (where the chick still reaches 8 kg after 90 d) would increase by more than 25%.     

A new automated logging gateway to study the demographics of macaroni penguins (Eudyptes chrysolophus) at Bird Island, South Georgia: testing the reliability of the system using radio telemetry

The use of automated systems to record the identity of individual penguins and their movements in and out of a colony can provide an effective means of studying penguin biology remotely. A new gateway installed at the macaroni penguin colony at Fairy Point (513 breeding pairs in 2003) on Bird Island, South Georgia in February 2003 and the implantation of passive integrated transponders for identifying individuals is described. The reliability of the system in recording penguin arrival and departure during the end of the 2002/2003 breeding season and over the complete 2003/2004 breeding season was tested using an independent method of radio telemetry. Results from two seasons of trials indicated that there was only a 3.7% probability of the gateway missing a penguin in 2002/2003 (185 total logged crossings) and 3.9% in 2003/2004 (1,309 total logged crossings); this compared with probabilities of 16.2 and 7.9% using radio telemetry, both differences being highly significant. This automatic logging gateway is therefore shown to be a more reliable means of recording the transit of penguins between the colony and sea and, over the longer term, elucidating colony attendance and survival rates of this species at South Georgia.     

Dynamics of antarctic penguin populations in relation to inter-annual variability in sea ice distribution

To investigate the role of sea ice cover on penguin populations we used principal component analysis to compare population variables of Adélie (Pygoscelis adeliae) and chinstrap (Pygoscelis antarctica) penguins breeding on Signy Island, South Orkney Islands with local (from direct observations) and regional (from remote sensing data) sea ice variables. Throughout the study period, the Adélie penguin population size remained stable, whereas that of chinstrap penguins decreased slightly. For neither species were there significant relationships between population size and breeding success, except for an apparent inverse density-dependent relationship between the number of Adélie breeding pairs and the number of eggs hatching. For both species, no general relationship was found between either population size or breeding success and the local sea ice conditions. However, the regional sea ice extent at a particular time prior to the start of the breeding season was related to the number of birds that arrived to breed. For both species, this period occurred before the sea ice reached its maximum extent and was slightly earlier for Adélie than for chinstrap penguins. These results suggest that sea ice conditions outside the breeding season may play an important role in penguin population processes.     

Diet and reproductive success of Adélie and chinstrap penguins: linking response of predators to prey population dynamics

The diet and reproductive performance of two sympatric penguin species were studied at Signy Island, South Orkney Islands between 1997 and 2001. Each year, Adélie (Pygoscelis adeliae) and chinstrap (P. antarctica) penguins fed almost exclusively (>99% by mass) on Antarctic krill; however, there was considerable inter-annual variation in reproductive output. In 1998, chinstrap penguins were adversely affected by extensive sea-ice in the vicinity of the colony, whereas Adélie penguins were unaffected by this. However, in 2000, both species suffered reduced reproductive output. Detailed analysis of the population-size structure of krill in the diet indicated a lack of recruitment of small krill into the population since 1996. A simple model of krill growth and mortality indicated that the biomass represented by the last recruiting cohort would decline dramatically between 1999 and 2000. Thus, despite the lack of a change in the proportion of krill in the diet, the population demographics of the krill population suggested that the abundance of krill may have fallen below the level required to support normal breeding success of penguins sometime before or during the 2000 breeding season. The role of marine predators as indicator species is greatly enhanced when studies provide data reflecting not only the consequences of changes in the ecosystem but also those data that elucidate the causes of such changes.     

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.     

Comparison of population numbers of yellow-eyed penguins,

During a comprehensive survey in 1999, 2000 and 2001, we investigated the number of breeding yellow-eyed penguin pairs on Stewart Island, where cats are present, and on adjacent cat-free islands. We found 79 pairs of yellow-eyed penguin breeding in 19 discrete locations on Stewart Island (4.2 pairs per location), and 99 pairs breeding in 10 discrete locations on all cat-free islands (9.9 pairs per location). Large-scale humaninduced habitat modifications have not occurred on Stewart Island, nor on any of its adjacent offshore islands. While the extensive coastline of Stewart Island (673 km) offers potentially large areas of breeding habitat for penguins, the highest number of breeding pairs were found on the smaller, predator-free Codfish Island (25 km coastline), where a total of 61 breeding pairs were recorded. On Stewart Island, where mustelids do not occur, only feral cats can pose a serious threat to penguin offspring. Results from this study suggest that feral cats may prey on yellow-eyed penguins on Stewart Island. Further work is necessary to investigate whether the observed low numbers of yellow-eyed penguins on Stewart Island are caused by feral cat predation. If so, it may be possible to develop appropriate measures to protect this penguin species from a population decline.     

Diurnal sleep depth changes in the king penguin (<Emphasis Type="Italic">Aptenodytes patagonicus</Emphasis>)

Avian sleep quality depends on its depth (deeper sleep being of better quality). In king penguins (Aptenodytes patagonica), sleep may be disturbed by congeners passing in the sleeper's vicinity. As king penguin activity is increased in the morning, sleep disturbances are more likely to occur during this time period. One might therefore assume that afternoon sleepers (AS) sleep more profoundly than morning sleepers (MS). To test this hypothesis, we examined the diurnal variations in sleep depth of king penguins sleeping in resting sites adjacent to the colony of 'La Baie du Marin' (Crozet Archipelago). We measured the bodily tactile arousal threshold at the upper back level. The arousal threshold in AS was twice as high as in MS. This study demonstrates for the first time that sleep depth changes according to time of day in a diurnal wild bird. We postulate that diurnal sleep depth is increased due to decreased congener movements close to the sleeping penguin.