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Monitoring of population sizes and trends using conventional surveys is challenging for nocturnal, burrow-nesting seabirds. The White-chinned Petrel is the most commonly killed species in Southern Ocean fisheries and its breeding success at many sites is reduced because of predation by invasive cats and rodents. As adaptive management of such threats requires cost-effective and reproducible protocols for monitoring populations, we examined the potential of automated bioacoustic techniques for measuring colony attendance patterns (relative number of birds visiting at a given time) using data from acoustic recorders deployed over a breeding season at Bird Island, South Georgia. Generic recognition software was of limited utility, but a suite of acoustic indices in a random forest model reliably predicted the occurrence of vocalisations. Vocal activity showed clear temporal patterns, despite high day-to-day variability, and was lowest during the pre-laying period, in the early evening, and on moonlit nights. To facilitate estimation of population density using acoustic recorders, we determined the mean vocalisation rate of individuals (2.3 min−1), mean call length (~15.3 sec), and detection distance (~15 m based on signal to noise ratios of playbacks). Our results indicate that acoustic indices are a useful measure of colony attendance. If these indices can be linked to density, acoustic monitoring would provide a powerful and cost-effective census method for White-chinned Petrels and other nocturnal species. [ABSTRACT FROM AUTHOR]

Interspecific introgression can occur between species that evolve rapidly within an adaptive radiation. Pachyptila petrels differ in bill size and are characterised by incomplete reproductive isolation, leading to interspecific gene flow. Salvin's prion (Pachyptila salvini), whose bill width is intermediate between broad-billed (P. vittata) and Antarctic (P. desolata) prions, evolved through homoploid hybrid speciation. MacGillivray's prion (P. macgillivrayi), known from a single population on St Paul (Indian Ocean), has a bill width intermediate between salvini and vittata and could also be the product of interspecies introgression or hybrid speciation. Recently, another prion population phenotypically similar to macgillivrayi was discovered on Gough (Atlantic Ocean), where it breeds 3 months later than vittata. The similarity in bill width between the medium-billed birds on Gough and macgillivrayi suggest that they could be closely related. In this study, we used genetic and morphological data to infer the phylogenetic position and evolutionary history of P. macgillivrayi and the Gough medium-billed prion relative other Pachyptila taxa, to determine whether species with medium bill widths evolved through common ancestry or convergence. We found that Gough medium-billed prions belong to the same evolutionary lineage as macgillivrayi, representing a new population of MacGillivray's prion that originated through a colonisation event from St Paul. We show that macgillivrayi's medium bill width evolved through divergence (genetic drift) and independently from that of salvini, which evolved through hybridisation (gene flow). This represents the independent convergence towards a similarly medium-billed phenotype. The newly discovered MacGillivray's prion population on Gough is of utmost conservation relevance, as the relict macgillivrayi population in the Indian Ocean is very small. [ABSTRACT FROM AUTHOR]

Ocean circulation connects geographically distinct ecosystems across a wide range of spatial and temporal scales via exchanges of physical and biogeochemical properties. Remote oceanographic processes can be especially important for ecosystems in the Southern Ocean, where the Antarctic Circumpolar Current transports properties across ocean basins through both advection and mixing. Recent tracking studies have indicated the existence of two large‐scale, open ocean habitats in the Southern Ocean used by grey petrels (Procellaria cinerea) from two populations (i.e., Kerguelen and Antipodes islands) during their nonbreeding season for extended periods during austral summer (i.e., October to February). In this work, we use a novel combination of large‐scale oceanographic observations, surface drifter data, satellite‐derived primary productivity, numerical adjoint sensitivity experiments, and output from a biogeochemical state estimate to examine local and remote influences on these grey petrel habitats. Our aim is to understand the oceanographic features that control these isolated foraging areas and to evaluate their ecological value as oligotrophic open ocean habitats. We estimate the minimum local primary productivity required to support these populations to be much <1% of the estimated local primary productivity. The region in the southeast Indian Ocean used by the birds from Kerguelen is connected by circulation to the productive Kerguelen shelf. In contrast, the region in the south‐central Pacific Ocean used by seabirds from the Antipodes is relatively isolated suggesting it is more influenced by local factors or the cumulative effects of many seasonal cycles. This work exemplifies the potential use of predator distributions and oceanographic data to highlight areas of the open ocean that may be more dynamic and productive than previously thought. Our results highlight the need to consider advective connections between ecosystems in the Southern Ocean and to re‐evaluate the ecological relevance of oligotrophic Southern Ocean regions from a conservation perspective. [ABSTRACT FROM AUTHOR]

The use of miniaturized electronic tracking devices has illuminated our understanding of seabird distributions and habitat use, and how anthropogenic threats interact with seabirds in both space and time. To determine the year‐round distribution of adult Campbell albatross (Thalassarche impavida), a single‐island endemic, breeding only at Campbell Island in New Zealand's subantarctic, a total of 68 year‐long location data sets were acquired from light‐based geolocation data‐logging tags deployed on breeding birds in 2009 and 2010.During the incubation and chick‐guard phases of the breeding season, birds used cool (<10°C) waters over the Campbell Plateau, but also ranged over deeper, shelf‐break and oceanic waters (4,000–5,500 m) beyond the Plateau. Later in the breeding season, during post‐guard chick‐rearing, Campbell albatrosses exploited generally deep waters (4,000–5,000 m) beyond the Campbell Plateau.During the non‐breeding period, adults tended to move northwards into warmer (approximately 15°C) waters and occupied areas beyond western Australia in the west to offshore from Chile in the east. Overall, about 30% of adults spent some of their non‐breeding period in the central and eastern Pacific Ocean, substantially expanding the previously reported range for this species.One bird, that failed in its breeding attempt in October 2009, departed Campbell Island and circumnavigated the southern oceans before being recaptured back at Campbell Island in October 2010. This is the first example of an annually‐breeding albatross species completing a circumnavigation between breeding attempts.Overlap with fishing effort, using data from the Global Fishing Watch database, was assessed on a monthly and seasonal basis. Generally, levels of overlap between Campbell albatross and fishing effort were relatively low during the breeding season but were approximately 60% higher during the non‐breeding period, underlining the need for international initiatives to safeguard this species. [ABSTRACT FROM AUTHOR]

In a highly dynamic airspace, flying animals are predicted to adjust foraging behaviour to variable wind conditions to minimize movement costs.Sexual size dimorphism is widespread in wild animal populations, and for large soaring birds which rely on favourable winds for energy‐efficient flight, differences in morphology, wing loading and associated flight capabilities may lead males and females to respond differently to wind. However, the interaction between wind and sex has not been comprehensively tested.We investigated, in a large sexually dimorphic seabird which predominantly uses dynamic soaring flight, whether flight decisions are modulated to variation in winds over extended foraging trips, and whether males and females differ.Using GPS loggers we tracked 385 incubation foraging trips of wandering albatrosses Diomedea exulans, for which males are c. 20% larger than females, from two major populations (Crozet and South Georgia). Hidden Markov models were used to characterize behavioural states—directed flight, area‐restricted search (ARS) and resting—and model the probability of transitioning between states in response to wind speed and relative direction, and sex.Wind speed and relative direction were important predictors of state transitioning. Birds were much more likely to take off (i.e. switch from rest to flight) in stronger headwinds, and as wind speeds increased, to be in directed flight rather than ARS. Males from Crozet but not South Georgia experienced stronger winds than females, and males from both populations were more likely to take‐off in windier conditions.Albatrosses appear to deploy an energy‐saving strategy by modulating taking‐off, their most energetically expensive behaviour, to favourable wind conditions. The behaviour of males, which have higher wing loading requiring faster speeds for gliding flight, was influenced to a greater degree by wind than females. As such, our results indicate that variation in flight performance drives sex differences in time–activity budgets and may lead the sexes to exploit regions with different wind regimes. [ABSTRACT FROM AUTHOR]

Diet analyses can reveal important changes in seabird foraging ecology and, by inference, resource availability and predator–prey dynamics within the wider marine ecosystem. Here, we analysed stomach contents of 1544 grey-headed albatross Thalassarche chrysostoma (GHA) and black-browed albatross T. melanophris (BBA) chicks from Bird Island, South Georgia. We describe dietary shifts (1996–2017), and link those to annual prey availability indices and breeding success. Annual variability in diet was high, and long-term trends in the main components were broadly similar in both albatrosses. Fish consumption (by mass) generally increased over time. Mackerel icefish Champsocephalus gunnari occurrence increased in GHA diets, but was unrelated to local densities derived from fisheries/research cruises. Cephalopod consumption declined until the early 2000s, then plateaued, and the occurrence of the ommastrephid squid Martialia hyadesi declined over time in both albatrosses. In BBAs, Antarctic krill Euphausia superba consumption decreased over time. Conversely, Antarctic krill consumption by GHAs increased until the early 2000s, decreased until the mid-2010s, and increased again in 2017. Antarctic krill consumption was unrelated to local densities based on acoustic surveys, and did not correlate with breeding success. Remotely sensed chlorophyll-a within core foraging areas showed a positive relationship with Antarctic krill in GHA diets, but a negative relationship with M. hyadesi occurrence in both albatross diets. Dietary shifts had consequences for GHA breeding success, which was negatively related to the importance of the cranchiid Galiteuthis glacialis and positively related to M. hyadesi importance. These results highlight the complex mechanisms linking prey availability, diet and breeding success in albatrosses. [ABSTRACT FROM AUTHOR]

Albatrosses (Diomedeidae) are iconic pelagic seabirds whose life-history traits (longevity, high trophic position) put them at risk of high levels of exposure to methylmercury (MeHg), a powerful neurotoxin that threatens humans and wildlife. Here, we report total Hg (THg) concentrations in body feathers from 516 individual albatrosses from 35 populations, including all 20 taxa breeding in the Southern Ocean. Our key finding is that albatrosses constitute the family of birds with the highest levels of contamination by Hg, with mean feather THg concentrations in different populations ranging from moderate (3.8 μg/g) to exceptionally high (34.6 μg/g). Phylogeny had a significant effect on feather THg concentrations, with the mean decreasing in the order Diomedea  >  Phoebetria  >  Thalassarche . Unexpectedly, moulting habitats (reflected in feather δ 13 C values) was the main driver of feather THg concentrations, indicating increasing MeHg exposure with decreasing latitude, from Antarctic to subtropical waters. The role of moulting habitat suggests that the majority of MeHg eliminated into feathers by albatrosses is from recent food intake ( income strategy). They thus differ from species that depurate MeHg into feathers that has been accumulated in internal tissues between two successive moults ( capital strategy). Since albatrosses are amongst the most threatened families of birds, it is noteworthy that two albatrosses listed as Critical by the World Conservation Union (IUCN) that moult and breed in temperate waters are the most Hg-contaminated species (the Amsterdam and Tristan albatrosses). These data emphasize the urgent need for robust assessment of the impact of Hg contamination on the biology of albatrosses and they document the high MeHg level exposure of wildlife living in the most remote marine areas on Earth. [ABSTRACT FROM AUTHOR]

We present the first detailed data on the distribution and migration patterns of four pelagic seabird species in the Eastern Indian Ocean—the Lesser Noddy (Anous tenuirostris melanops), Brown Noddy (Anous stolidus), Wedge-tailed Shearwater (Ardenna pacifica) and Bridled Tern (Onychoprion anaethetus) breeding at the Houtman Abrolhos and the Wedge-tailed Shearwater breeding at Varanus Island, Western Australia—tracked using geolocators during their respective non-breeding periods. Lesser Noddies remained largely in the general vicinity or slightly to the south of the colony in their non-breeding season (February-September). Brown Noddies spent their non-breeding period (March-August) in the Northwest Shelf area of Western Australia, around 950 km north of the colony. In contrast, Bridled Terns and most Wedge-tailed Shearwaters undertook extensive non-breeding migrations. Wedge-tailed Shearwaters occupied waters adjacent or to the north of their nesting sites or migrated 4200 km northwest into the equatorial central Indian Ocean near the Ninety East Ridge during the non-breeding season (late April to mid-November). These same areas were used during the sabbatical summer by Wedge-tailed Shearwaters that had deferred breeding. Bridled Terns spent their non-breeding period (April-September) in the Celebes Sea, 3800 km north of the Houtman Abrolhos. The results are discussed in the context of potential marine threats to the different species during the non-breeding period. [ABSTRACT FROM AUTHOR]

The Arctic is a highly seasonal environment with a harsh climate and extensive sea ice cover during the winter. Consequently, most Arctic-breeding seabirds migrate south to reach more benign environmental conditions. Knowledge of migration routes and wintering areas is integral for successful conservation of these globally important breeding populations. In this study, we deployed light-level geolocators on female common eiders Somateria mollissima breeding in Kongsfjorden, Svalbard, to track movements during the non-breeding season. We retrieved functioning loggers from 47 individual birds in 2009-2013 and mapped their migration routes and wintering areas. Thirty-six birds (77 %) wintered around the Icelandic coast and 11 (23 %) off the coasts of North Norway. Autumn migration took place between late August and late December, and spring migration from late March to late May. The migration (ca 1700 km to Iceland and 1300 km to North Norway) lasted for about 4 days in autumn and 3 days in spring. Later arrival resulted in later nest initiation, implying a carry-over effect of winter conditions on subsequent breeding. Birds that migrated to Norway departed later from Svalbard in autumn and consequently spent less time in the wintering area than individuals that migrated to Iceland. As just two countries, Iceland and Norway, appear to host all common eiders from Svalbard during the winter, the new information provided by this study on the core areas and timing of migration should provide the impetus for improved bilateral conservation management of this important Arctic breeding population of common eiders. [ABSTRACT FROM AUTHOR]