Jean-Baptiste Thiebot

Where do penguins go during the inter-breeding period? Using geolocation to track the winter dispersion of the macaroni penguin.

Although penguins are key marine predators from the Southern Ocean, their migratory behaviour during the inter-nesting period remains widely unknown. Here, we report for the first time, to our knowledge, the winter foraging movements and feeding habits of a penguin species by using geolocation sensors fitted on penguins with a new attachment method. We focused on the macaroni penguin Eudyptes chrysolophus at Kerguelen, the single largest consumer of marine prey among all seabirds. Overall, macaroni penguins performed very long winter trips, remaining at sea during approximately six months within the limits of the Southern Ocean. They departed from Kerguelen in an eastward direction and distributed widely, over more than 3.106 km2. The penguins spent most of their time in a previously unrecognized foraging area, i.e. a narrow latitudinal band (47–49° S) within the central Indian Ocean (70–110° E), corresponding oceanographically to the Polar Frontal Zone. There, their blood isotopic niche indicated that macaroni penguins preyed mainly upon crustaceans, but not on Antarctic krill Euphausia superba, which does not occur at these northern latitudes. Such winter information is a crucial step for a better integrative approach for the conservation of this species whose world population is known to be declining.

Coexistence of oceanic predators on wintering areas explained by population-scale foraging segregation in space or time

Ecological niche theory predicts segregation mechanisms that mitigate potential competition between closely related organisms. However, little is known outside the breeding season, when central-place foraging animals may move on larger scales. This study tested for segregation mechanisms within the same 2007 inter-breeding period on three neighboring populations of avian predators from the southern Indian Ocean: Eastern Rockhopper Penguins Eudyptes filholi from Crozet and Kerguelen and Northern Rockhopper Penguins E. moseleyi from Amsterdam. Using state-of-the-art geolocation tracking and stable isotope analysis techniques, we quantified and compared the ecological niches in time, space, and diet. The three populations showed large-scale movements over deep oceanic waters near the Subantarctic Front, with generally little individual variation. The two neighboring populations of Eastern Rockhopper Penguins showed strikingly distinct distribution in space, while foraging in similar habitats and at the same trophic level (crustacean-eaters). In contrast, Northern Rockhoppers showed marked spatial overlap with birds of the sibling Eastern species, but their temporal delay of two months enabled them to effectively avoid significant overlap. Our results highlight parsimonious mechanisms of resource partitioning operating at the population level that may explain how animals from neighboring localities can coexist during the nonbreeding period.

Larger foraging range but similar habitat selection in non-breeding versus breeding sub-Antarctic penguins

Abstract For land-breeding marine organisms such as seabirds, knowledge about their habitat use has mainly been gained through studies of breeding individuals that are constrained to return frequently to their breeding grounds. In this study we set out to measure whether: a) habitat selection in the non-breeding period predicts habitat selection in the breeding period, and b) whether breeding individuals concentrated their activity on the closest suitable habitats. Macaroni Eudyptes chrysolophus and gentoo Pygoscelis papua penguins, two marine predators with contrasting foraging strategies, were tracked from the Iles Kerguelen and their habitat selection investigated through Mahalanobis distances factorial analysis. This study presents the first data about gentoo penguins’ juvenile dispersal. For both species, results showed 6.9 times larger maximum ranges and up to 12.2 times greater distances travelled during the non-breeding period. Habitat suitability maps suggested both species made similar environmental selections whatever the period. Macaroni penguins targeted pelagic areas beyond the shelf break while gentoo penguins always remained over the shelf. We consider the ecological significance of larger scale movements made outside the breeding period and suggest that this non-breeding period is of particular interest when attempting to understand an animals habitat selection.

Contrasted associations between seabirds and marine mammals across four biomes of the southern Indian Ocean

AbstractSeabirds associations with marine mammals have been shown to be an efficient way by which the seabirds can detect and access prey patches. However, these associations have been documented locally in the literature and their relevance at the ecosystem level is unknown, mostly because they constitute relatively rare events and therefore few appropriate data exist. In this study, we aimed at quantifying and qualifying these interactions, based on long-term standardised at-sea observations carried out from 1978 to 2005 in the whole southern Indian Ocean. We (1) investigated whether the observed interspecific associations between foraging seabirds and marine mammals could be distinguished from chance using a bootstrap method, and (2) compared their occurrences between four oceanic biomes sampled (tropical, subtropical, subantarctic, Antarctic). Although in our data we could not discriminate active association versus aggregation of species feeding on the same prey patches, our results indicate that, in each biome, 5–10 seabird species were more frequently associated with marine mammals than expected due to chance. Tropical birds appeared to be associated almost exclusively with Delphinidae schools, whereas in the subtropical waters, all the significant associations occurred with marine mammals others than dolphins. In the subantarctic biome, seabirds were mostly associated with Pinnipeds, and the highly productive Antarctic waters provided opportunities for diverse but rare associations. This study suggests that the ecological links between foraging predators can be measured using a randomisation method, and provides conclusive and comparative information on the ecology of apex trophic levels organisms from pelagic communities.ZusammenfassungVergleich von Vergesellschaftungen zwischen Seevögeln und Meeressäugern über vier Biome des südlichen Indischen Ozeans hinweg Vergesellschaftungen von Seevögeln mit Meeressäugern sind eine effiziente Methode für die Seevögel, um Beute zu finden und zu nutzen. Allerdings wurden solche Vergesellschaftungen in der Literatur nur lokal dokumentiert, und ihre Relevanz auf Ökosystemebene ist unbekannt, vor allem, weil sie relativ seltene Vorkommnisse darstellen und es daher nur wenig angemessene Daten gibt. In dieser Untersuchung versuchten wir, diese Interaktionen quantitativ und qualitativ zu beschreiben auf der Basis von standardisierten Langzeit-Beobachtungen auf See, die zwischen 1978 und 2005 im gesamten südlichen Indischen Ozean durchgeführt wurden. Wir (1) untersuchten mit Hilfe einer Bootstrap-Methode, ob sich die beobachteten interspezifischen Vergesellschaftungen zwischen Seevögeln und Meeressäugern von zufälligen Ereignissen unterscheiden ließen und (2) verglichen deren Vorkommen zwischen den vier untersuchten ozeanischen Biomen (tropisch, subtropisch, subantarktisch, antarktisch). Obwohl wir in unseren Daten nicht zwischen aktiver Vergesellschaftung und einer Ansammlung von Arten unterscheiden konnten, die zufällig in den selben Beutefeldern jagten, deuten unsere Ergebnisse doch darauf hin, dass in jedem Biom fünf bis zehn Seevogelarten häufiger mit Meeressäugern vergesellschaftet waren als zufällig erwartet. Tropische Vögel schienen fast ausschließlich mit Schulen von Delphinidae vergesellschaftet zu sein, während in subtropischen Gewässern alle wesentlichen Vergesellschaftungen mit anderen Meeressäugern als Delphinen stattfanden. Im subarktischen Biom waren Seevögel meist mit Robben vergesellschaftet, und die hochproduktiven antarktischen Gewässer boten Möglichkeiten zu verschiedenen, aber seltenen, Vergesellschaftungen. Diese Untersuchung legt nahe, dass die ökologischen Verbindungen zwischen jagenden Prädatoren mit Hilfe einer Randomisierungsmethode gemessen werden können und liefert schlüssige und vergleichende Information über die Ökologie von in der Nahrungskette hoch stehenden Organismen aus pelagischen Gemeinschaften.

A space oddity: Geographic and specific modulation of migration in Eudyptes penguins

Post-breeding migration in land-based marine animals is thought to offset seasonal deterioration in foraging or other important environmental conditions at the breeding site. However the inter-breeding distribution of such animals may reflect not only their optimal habitat, but more subtle influences on an individual’s migration path, including such factors as the intrinsic influence of each locality’s paleoenvironment, thereby influencing animals’ wintering distribution. In this study we investigated the influence of the regional marine environment on the migration patterns of a poorly known, but important seabird group. We studied the inter-breeding migration patterns in three species of Eudyptes penguins (E. chrysolophus, E. filholi and E. moseleyi), the main marine prey consumers amongst the World’s seabirds. Using ultra-miniaturized logging devices (light-based geolocators) and satellite tags, we tracked 87 migrating individuals originating from 4 sites in the southern Indian Ocean (Marion, Crozet, Kerguelen and Amsterdam Islands) and modelled their wintering habitat using the MADIFA niche modelling technique. For each site, sympatric species followed a similar compass bearing during migration with consistent species-specific latitudinal shifts. Within each species, individuals breeding on different islands showed contrasting migration patterns but similar winter habitat preferences driven by sea-surface temperatures. Our results show that inter-breeding migration patterns in sibling penguin species depend primarily on the site of origin and secondly on the species. Such site-specific migration bearings, together with similar wintering habitat used by parapatrics, support the hypothesis that migration behaviour is affected by the intrinsic characteristics of each site. The paleo-oceanographic conditions (primarily, sea-surface temperatures) when the populations first colonized each of these sites may have been an important determinant of subsequent migration patterns. Based on previous chronological schemes of taxonomic radiation and geographical expansion of the genus Eudyptes, we propose a simple scenario to depict the chronological onset of contrasting migration patterns within this penguin group.

Mates but not sexes differ in migratory niche in a monogamous penguin species

Strong pair bonds generally increase fitness in monogamous organisms, but may also underlie the risk of hampering it when re-pairing fails after the winter season. We investigated whether partners would either maintain contact or offset this risk by exploiting sex-specific favourable niches during winter in a migratory monogamous seabird, the southern rockhopper penguin Eudyptes chrysocome. Using light-based geolocation, we show that although the spatial distribution of both sexes largely overlapped, pair-wise mates were located on average 595 ± 260 km (and up to 2500 km) apart during winter. Stable isotope data also indicated a marked overlap between sex-specific isotopic niches (δ13C and δ15N values) but a segregation of the feeding habitats (δ13C values) within pairs. Importantly, the tracked females remained longer (12 days) at sea than males, but all re-mated with their previous partners after winter. Our study provides multiple evidence that migratory species may well demonstrate pair-wise segregation even in the absence of sex-specific winter niches (spatial and isotopic). We suggest that dispersive migration patterns with sex-biased timings may be a sufficient proximal cause for generating such a situation in migratory animals.

Do Introduced Mammals Chronically Impact the Breeding Success of the World's Rarest Albatross?

Abstract Introduced mammals may have deleterious effects on avifauna. We investigated whether such species may be affecting the breeding success of the critically endangered Amsterdam Albatrosses Diomedea amsterdamensis on its remote breeding island. Twelve camera-traps deployed near albatross nests during the chick brooding period in 2011 captured 25,000 pictures. Two of them showed Black Rats Rattus rattus, but without revealing evidence of any direct interaction between the two species. Breeding success in 2011 was similar to that in previous years (60%). Our survey suggests that introduced mammals may not currently represent a primary direct threat to this population, but they might amplify the risks of chick mortality in case of disease outbreaks.

The rime of the modern mariner: evidence for capture of yellow-nosed albatross from Amsterdam Island in Indian Ocean longline fisheries

Abstract Commercial fisheries currently pose a serious threat at sea to the conservation of a number of pelagic seabirds. However, these interactions are complex, and reports on population-specific bycatch in the high seas are scarce. Here we report the case of an Indian yellow-nosed albatross Thalassarche carteri re-sighted on Amsterdam Island after an apparent capture by an Indonesian long-liner, as indicated by a message attached to the bird. This record demonstrates that Amsterdam birds may interact with long-liners indeed, at least during winter, and that such interactions are not systematically lethal. We suggest that bycatch sub-lethal effects should be investigated at colonies with high risks of individual capture at sea.

Avian cholera outbreaks threaten seabird species on Amsterdam Island

Infectious diseases may be particularly critical for the conservation of endangered species. A striking example is the recurrent outbreaks that have been occurring in seabirds on Amsterdam Island for the past 30 years, threatening populations of three Endangered seabird species and of the endemic, Critically Endangered Amsterdam albatross Diomedea amsterdamensis. The bacteria Pasteurella multocida (avian cholera causative agent), and to a lesser extent Erysipelothrix rhusiopathiae (erysipelas causative agent), were both suspected to be responsible for these epidemics. Despite this critical situation, demographic trends were not available for these threatened populations, and the occurrence and characterization of potential causative agents of epizootics remain poorly known. The aims of the current study were to (i) provide an update of population trends for four threatened seabird species monitored on Amsterdam Island, (ii) assess the occurrence of P. multocida, and E. rhusiopathiae in live birds from five species, (iii) search for other infectious agents in these samples and, (iv) isolate and genotype the causative agent(s) of epizooties from dead birds. Our study shows that the demographic situation has worsened substantially in three seabird species during the past decade, with extremely low reproductive success and declining populations for Indian yellow-nosed albatrosses Thalassarche carteri, sooty albatrosses Phoebetria fusca, and northern rockhopper penguins Eudyptes moseleyi. Pasteurella multocida or E. rhusiopathiae were detected by PCR in live birds of all five investigated species, while results were negative for eight additional infectious agents. A single strain of P. multocida was repeatedly cultured from dead birds, while no E. rhusiopathiae could be isolated. These results highlight the significance of P. multocida in this particular eco-epidemiological system as the main agent responsible for epizootics. The study stresses the urgent need to implement mitigation measures to alter the course of avian cholera outbreaks threatening the persistence of seabird populations on Amsterdam Island.

A Comparison of Direct and Distance Sampling Methods to Estimate Abundance of Nesting Gulls

Summary. We compared the performances of the strip transect count method and the distance sampling method during colony surveys of large gulls to estimate the total number of nests. Ten colonies were surveyed by both methods. Nest detection probabilities varied from 0.519 ± 0.064 to 0.706 ± 0.049 and the average nest detection probability was 0.614 ± 0.015. Nest densities were highly variable, ranging from 77 nests/ha to 717 nests/ha. Estimates of the number of nests obtained by the strip transect count method averaged 9.3% lower than those obtained by distance sampling but by as much as 31% in some colonies. Underestimation by the strip transect counts increased at high nest densities (Kendall t = -0.556, P = 0.032). The strip transect method needed on average 6.5 observers per colony surveyed, whereas the distance sampling method required 1.4 observers per colony. In addition, the mean time spent per colony was 3 hours vs 1.7 hours for the strip transect and distance sampling methods respectively. Combining both these measures of effort, distance sampling required on average 87% less effort in the field than the strip transect method. We strongly advocate the use of distance sampling for surveys of large gull colonies.