Differences in foraging habitat result in contrasting fisheries interactions in two albatross populations

Albatrosses attend fishing boats to feed on fishing discards but are often at risk of accidental bycatch. To examine whether populations (same species) and sexes differ in their overlap with fisheries due to differences in habitat use, we combined the use of recently developed loggers equipped with GPS and boat radar detectors with Automatic Identification System (AIS) data. Our study indicates that incubating wandering albatrosses Diomedea exulans from Crozet and Kerguelen foraged in different habitats although the duration of trips was similar. Both female and male Kerguelen birds took advantage of the large and productive surrounding shelf, whereas Crozet birds used the small shelf around the islands to a lesser extent. In Crozet, there was segregation between males and females, the latter favouring deeper and warmer waters. The 2 strategies of habitat use led to different overlap and attraction to boats, with Kerguelen birds encountering and attending boats for longer and at closer proximity to the colony than Crozet birds. Crozet females encountered boats at greater distances from the colony than males. Because of their different habitat use and foraging outside exclusive economic zones (EEZ) and further from the colony, Crozet birds attended more non-declared boats (without AIS) than Kerguelen birds. Albatrosses were more attracted by fisheries than cargo vessels and were especially attracted by fishing discards that led them to attend vessels for longer periods for both sexes and populations. The differences found between populations and individuals in terms of habitat specialization and encounter rate of fisheries should be considered for future assessments of risk of bycatch.

Variation among colonies in breeding success and population trajectories of wandering albatrosses Diomedea exulans at South Georgia

The wandering albatross, Diomedea exulans, is a globally threatened species breeding at a number of sites within the Southern Ocean. Across the South Georgia archipelago, there are differences in population trends even at closely located colonies. Between 1999 and 2018 the largest colony, at Bird Island, declined at 3.01% per annum, while in the Bay of Isles, the decline was 1.44% per annum. Using mean demographic rates from a 31-year study at Bird Island and an 11-year study of breeding success at Prion Island in the Bay of Isles in a VORTEX model, we show that differences in breeding success do not fully explain observed differences in population trends. Other potential contributing factors are differential use of foraging areas, with possible knock-on effects on adult body condition, provisioning rate and breeding success, or on bycatch rates of adults or immatures.

Reconstrucción alométrica de la capacidad de vuelo de Pelagornis chilensis Mayr & Rubilar-Rogers, 2010 (Aves: Pelagornithidae)

Las aves fósiles de la familia Pelagornithidae fueron grandes aves marinas planeadoras que habitaron desde el Paleoceno tardío hasta el Plioceno. En este trabajo se estudia la capacidad de vuelo de Pelagornis chilensis, una especie de esa familia. Utilizando la fórmula de sustentación y fórmulas alométricas se demostró que diferentes tipos de velocidades del ave extinta son significativamente mayores a las de Thalassarche chrysostoma, el albatros de cabeza gris, el ave marina actual que más se asemeja morfológicamente al ave extinta. Además, en coherencia con los resultados anteriores, se determinó que la potencia parásita, la potencia inducida, la fuerza muscular y el número de Reynolds de P. chilensis son significativamente mayores que las de T. chrysostoma. El método fue utilizado en el albatros Diomedea exulans para comprobar la cercanía de los valores observados con los calculados y estimar un porcentaje de error. La diferencia obtenida entre estos resultados es de un 2,7%, demostrando la efectividad del método. Finalmente, se estudian las condiciones y forma de vuelo de los grandes albatros y su posible aplicación al vuelo de los Pelagornítidos. Se hipotetiza que por el gran tamaño de las especies estudiadas y por tener una morfología semejante, dichos patrones de vuelo serían similares.

Long-term changes in habitat and trophic level of Southern Ocean squid in relation to environmental conditions

Long-term studies of pelagic nekton in the Southern Ocean and their responses to ongoing environmental change are rare. Using stable isotope ratios measured in squid beaks recovered from diet samples of wandering albatrosses Diomedea exulans, we assessed decadal variation (from 1976 to 2016) in the habitat (δ13C) and trophic level (δ15N) of five important Southern Ocean squid species in relation to indices of environmental conditions—Southern Oscillation Index (SOI) and Southern Annular Mode (SAM). Based on δ13C values, corrected for the Suess effect, habitat had changed over the last 50 years for Taonius sp. B (Voss), Gonatus antarcticus, Galiteuthis glacialis and Histioteuthis atlantica but not Moroteuthopsis longimana. By comparison, mean δ15N values were similar across decades for all five species, suggesting minimal changes in trophic levels. Both SAM and SOI have increased in strength and frequency over the study period but, of the five species, only in Taonius sp. B (Voss) did these indices correlate with, δ13C and δ15N values, indicating direct relationships between environmental conditions, habitat and trophic level. The five cephalopod species therefore changed their habitats with changing environmental conditions over the last 50 years but maintained similar trophic levels. Hence, cephalopods are likely to remain important prey for top predators in Southern Ocean food webs, despite ongoing climate change.

Acuariidae (Nematoda) in Procellariiformes (Aves) on the southern coast of Rio Grande do Sul, Brazil

Acuariidae nematodes are normally found in the digestive tract of aquatic birds, including Procellariiformes. Were examined Calonectris borealis (n = 4), Diomedea exulans (n = 1), Macronectes giganteus (n = 8), Thalassarche chlororhynchos (n = 5), Thalassarche melanophrys (n = 15), Procellaria aequinoctialis (n = 4), Puffinus gravis (n = 2) and Puffinus puffinus (n = 6), collected on the southern coast of RS, Brazil. A total of 16 birds (35.5%) were parasitized by two species of Acuariidae. Stegophorus diomedeae and Seuratia shipleyi were identified, with prevalences of 26.1% and 21.7%, respectively. Few studies on nematodes in Procellariiformes have been conducted. Here, the acuariids Seuratia shipleyi in Calonectris borealis and Procellaria aequinoctialis and Stegophorus diomedeae in Diomedea exulans, Procellaria aequinoctialis and Thalassarche chlororhynchos were reported for the first time.

Progressive ontogenetic niche shift over the prolonged immaturity period of wandering albatrosses

Very little is known about trophic ontogenetic changes over the prolonged immaturity period of long-lived, wide-ranging seabirds. By using blood and feather trophic tracers (δ 13 C and δ 15 N, and mercury, Hg), we studied age-related changes in feeding ecology during the immature phase of wandering albatrosses Diomedea exulans when they gradually change from a pure oceanic life to visits to their future breeding grounds. Immatures fed in subtropical waters at high trophic positions during moult. Between- and within-individual variations in isotopic niche were very high, irrespective of age, highlighting wide-ranging exploratory behaviours. In summer, while acting as central-place foragers from their future breeding colony, individuals progressively relied on lower trophic level prey and/or southern latitudes as they aged, until occupying a similar isotopic niche to that of adults. Immatures had exceptionally high Hg burdens, with males having lower Hg concentrations than females, suggesting that they foraged more in subantarctic waters. Our findings suggest a progressive ontogenetic niche shift during central-place foraging of this long-lived species.

Settling the name Diomedea exulans Linnaeus, 1758 for the Wandering Albatross by neotypification

On-going conflict in use of the name Diomedea exulans Linnaeus, 1758 for different taxa of the great albatrosses (Wandering Albatross complex) is resolved by neotypification, fixing the name to the large subantarctic form formerly often known as D. chionoptera Salvin, 1896. Application of all scientific names in the complex is reviewed, an annotated synonymy for the large subantarctic form is provided, available names for smaller, temperate-zone forms are listed, and unavailable and otherwise invalid names referable to the complex are identified. Syntypes of D. chionoptera and D. spadicea J.F. Gmelin, 1789 are lectotypified as well, fixing their names as synonyms of D. exulans to prevent possible disturbance to in-use names for the smaller, temperate-zone forms.