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The use of miniaturized video cameras to study the at-sea behavior of flying seabirds has increased in recent years. These cameras allow researchers to record several behaviors that were not previously possible to observe. However, video recorders produce large amounts of data and videos can often be time-consuming to analyze. We present a new technique using open-source software to extract bank angles from bird-borne video footage. Bank angle is a key facet of dynamic soaring, which allows albatrosses and petrels to efficiendy search vast areas of ocean for food. Miniaturized video cameras were deployed on 28 Wandering Albatrosses (Diomedea exulans) on Marion Island (one of the two Prince Edward Islands) from 2016 to 2018. The OpenCV library for the Python programming language was used to extract the angle of the horizon relative to the bird's body (= bank angle) from footage when the birds were flying using a series of steps focused on edge detection. The extracted angles were not significantly different from angles measured manually by three independent observers, thus being a valid method to measure bank angles. Image quality, high wind speeds, and sunlight all influenced the accuracy of angle estimates, but post-processing eliminated most of these errors. Birds flew most often with cross-winds (58%) and tailwinds (39%), resulting in skewed distributions of bank angles when birds turned into the wind more often. Higher wind speeds resulted in extreme bank angles (maximum observed was 94°). We present a novel method for measuring postural data from seabirds that can be used to describe the fine-scale movements of the dynamic-soaring cycle. Birds appeared to alter their bank angle in response to varying wind conditions to counter wind drift associated with the prevailing westerly winds in the Southern Ocean. These data, in combination with fine-scale positional data, may lead to new insights into dynamic-soaring flight. El uso de cámaras de video en miniatura para estudiar el comportamiento en el mar de las aves marinas durante el vuelo ha aumentado en los últimos años. Estas cámaras permiten a los investigadores registrar varios comportamientos que antes no eran posible de observar. Sin embargo, las grabadoras de video producen grandes cantidades de datos y los videos a menudo pueden llevar mucho tiempo analizarlos. Presentamos una nueva técnica que utiliza software de código abierto para extraer los ángulos de inclinación de imágenes de videos. El ángulo de inclinación es una faceta clave para la dinámica de planeo, que permite a los albatros y petreles buscar alimentos en vastas áreas del océano. Las cámaras de video en miniatura se colocaron en 28 albatros errantes (Diomedea exulans) en la isla Marion (una de las dos islas del Príncipe Eduardo) entre 2016 y 2018. La biblioteca OpenCV para el lenguaje de programación Python se usó para extraer el ángulo del horizonte en relación con el cuerpo del ave (= ángulo de inclinación) del video cuando las aves volaban usando una serie de pasos centrados en la detección de bordes. Los ángulos extraídos no fueron significativamente diferentes de los ángulos medidos manualmente por tres observadores independientes, por lo que es un método válido para medir ángulos de banco. La calidad de la imagen, las altas velocidades del viento y la luz solar influyeron en la precisión de las estimaciones de ángulo, pero el procesamiento posterior eliminó la mayoría de estos errores. Las aves volaron con mayor frecuencia con vientos cruzados (58%) y vientos de cola (39%), lo que resulta en una distribución sesgada de los ángulos de las orillas cuando las aves giraron hacia el viento con más frecuencia. Las velocidades más altas del viento dieron como resultado ángulos extremos de inclinación (el máximo observado fue 94°). Presentamos un método novedoso para medir datos de posturas de aves marinas que se pueden usar para describir los movimientos a escala fina del ciclo dinámico del vuelo de planeo. Las aves parecen alterar su ángulo de inclinación en respuesta a las condiciones variables del viento para contrarrestar la deriva del viento asociada con los vientos predominantes del oeste en el Océano Austral. Estos datos, en combinación con datos posicionales a escala fina, pueden conducir a nuevas ideas sobre el vuelo de planeo dinámico.

Invasive rodents threaten native species in numerous ecosystems, especially oceanic islands. The House Mouse Mus musculus is the only introduced mammal species on sub-Antarctic Gough and Marion Islands. Ample evidence exists of mice preying upon seabird chicks on these two islands, but there have been only a few reports of attacks on adult seabirds, none of which has been fatal. We report the first deaths of adult great albatrosses due to mouse attacks. On Gough Island, three Tristan Albatrosses Diomedea dabbenena (Critically Endangered) brooding small chicks were observed with wounds typical of mouse attacks in March–April 2021; two likely abandoned their chick, causing breeding failure, and the third was found dead eight days after discovery with large blowfly larvae in the wound. On Marion Island, two wounded and eight dead adult Wandering Albatrosses D. exulans (Vulnerable) were found in April 2023. Inspection of the wounded individuals, as well as the injuries on the fresh carcasses strongly suggest that mouse predation was the cause of death. Gough Island is home to virtually all Tristan Albatrosses, and Marion Island is the single most important breeding site for Wandering Albatrosses, home to about a quarter of all breeding birds. The death of breeding adults of these long-lived species emphasizes the urgent need to eradicate introduced mice from these islands.

Invasive house mice Mus musculus are significant predators of seabird chicks on islands where they are the only introduced mammal, but there are very few records of attacks on adult birds. We report the first evidence of mouse attacks on adult albatrosses and petrels breeding on Marion and Gough Islands, where there has been a recent increase in attacks on seabird chicks. In September 2017, wounds consistent with a mouse attack were recorded on an incubating adult male Northern Giant Petrel Macronectes halli on Marion Island. The nest was deserted, and breeding success within 500 m was 18% (n = 11) compared to 68% at nests > 500 m away (n = 123), suggesting that other incubating adults in the immediate vicinity also might have been affected. In March 2018, an incubating Tristan Albatross Diomedea dabbenena was found on Gough Island with a typical mouse wound on its rump. The egg hatched and the same bird was later seen brooding and feeding the chick. In October 2018, an incubating Atlantic Yellow-nosed Albatross Thalassarche chlororhynchos was found on Gough Island with a wound on its back suggestive of a mouse attack and 23 freshly dead carcasses of this species were found, next to empty nests, in nearby colonies. These observations add to mounting evidence of the impacts of mice on seabirds, and further support calls to eradicate mice from Marion and Gough Islands

Seabirds are excellent ecosystem indicators and are amongst the most threatened taxa globally. Aldabra Atoll, Seychelles, supports significant breeding colonies of seabirds, especially red-footed boobies Sula sula . The population was surveyed by boat during 1968–1969 and in 2000, over which period the population grew from c. 6,500 to 10,000 breeding pairs. In 2022–2023, we monitored five subcolonies across Aldabra to determine breeding phenology and breeding success. In August 2022 and February 2023, we surveyed the atoll-wide population using the boat-based survey methodology followed in earlier studies. We also carried out unmanned aerial vehicle (UAV) surveys in February 2023 to compare the results with the boat-based counts and to quantify inland colonies undetectable by boat. Boat surveys revealed that Aldabra’s red-footed booby population had grown to 36,720 pairs by 2023, an increase that is intrinsically possible based on our population model but only if the much lower count in 2000 was an underestimate. The UAV and boat counts were closely aligned in our study, and aerial images captured a similar number of nests to boat surveys for shoreline colonies. However, UAV surveys revealed several undocumented inland colonies. An additional 5,574 inland breeding pairs of red-footed boobies were counted from images captured inland during aerial surveys in the 2023 wet season, bringing the atoll-wide population to at least 45,817 pairs. We recommend UAVs for surveys of large, conspicuous seabird species at low-lying mangrove colonies. Our study highlights the global importance of Aldabra as the most significant red-footed booby colony in the Indian Ocean and possibly the world.

Giant petrels Macronectes spp. are the largest avian predator-scavengers in the Southern Ocean and feed both by direct predation and by scavenging carrion. However, they are not considered to be predators of adult albatrosses. We report the first records of Southern Giant Petrels M. giganteus attacking and killing incubating Atlantic Yellow-nosed Albatrosses Thalassarche chlororhynchos on Gough Island. From 2017 to 2019, a total of 87 adult carcasses were found near nests within long-term monitoring areas. In 2019, 16 motion-activated cameras filmed 32 nests between September and January, during incubation up until chicks were no longer guarded by their parents. Camera footage revealed at least six different male Southern Giant Petrels independently attacking 11 incubating Atlantic Yellow-nosed Albatrosses, killing and feeding on 5 of those. We also recorded a Southern Giant Petrel attacking a brooding Atlantic Yellow-nosed Albatross and carrying its chick away. Of these camera-monitored nests breeding success was 18.75%, nest failure was due to parent mortality (n = 6), chick mortality (3) and nest abandonment (17), with giant petrels being confirmed or strongly suspected in at least 14 of 26 cases (54%). We observed these attacks in two out of 11 study areas, but it is uncertain whether this behaviour occurs elsewhere on Gough Island, or whether it is a novel hunting method learnt by a few individuals. However, if this behaviour spreads across albatross colonies, the resulting increase in adult mortality could have a significant impact on this endangered Atlantic Yellow-nosed Albatross population.

The southern oceans are home to a large variety of organisms, including many endemic species. High levels of endemism are due in part to non-physical barriers limiting gene flow in marine species. The sooty albatross Phoebetria fusca is an endangered seabird breeding on seven island groups in Atlantic and Indian Oceans. We sequenced the mitochondrial control region (55 birds) and genotyped 10 microsatellite markers (88 birds) to examine the population genetics of sooty albatrosses from Tristan da Cunha and Gough Island (Atlantic Ocean), and Marion Island, Île de la Possession (Crozet) and Amsterdam Island (Indian Ocean), which together support > 99% of the global population. We also analysed the bill sulcus colouration and quantified stable isotope composition of body feathers of breeding adults from Gough and Marion Islands. Both genetic markers identified two clusters separating sooty albatrosses breeding in the Atlantic and Indian Ocean basins. Standardized colour analysis also separated populations in the two ocean basins and revealed the sulcus of sooty albatrosses on Gough Island is significantly more yellow than individuals on Marion Island. Stable isotope analysis of body feathers showed significantly higher δ 13 C values from Marion sooty albatrosses compared to Gough conspecifics, indicating different moulting areas. Sooty albatrosses breeding on islands in the two ocean basins differ from each other in their genetics, morphology and ecological preferences. Accordingly, it is recommended that separate conservation management plans be implemented for sooty albatrosses breeding in each ocean basin to prevent the loss of evolutionarily significant units.

Pelagic seabirds often nest on islands that are far from productive foraging areas. The Procellariiformes (petrels, shearwaters and albatrosses) are among the longest-ranging seabirds; they have several adaptations that permit them to efficiently utilize distant foraging areas and fast for long periods during incubation (Phillips & Hamer 1999). Giant petrels ( Macronectes spp.) are large surface-nesting procellariiforms. They feed both by direct predation and by scavenging carrion, and they are the largest avian predator-scavengers in the Southern Ocean. Among procellariiform seabirds, one partner forages while their mate remains on the nest to incubate their single egg (Warham 1990). Northern giant petrels ( Macronectes halli ) have incubation shifts lasting up to 17 days (Cooper et al. 2001). In general, incubating procellariiform seabirds do not feed during their shift (Warham 1990). We report the first case to our knowledge of a procellariiform seabird, a northern giant petrel, actively feeding at its nest whilst incubating.

The continued decline in the small breeding population of southern elephant seals Mirounga leonina at Gough Island (40°19′S, 9°57′W) over a period of 46 years (1973–2019) signals the likely extirpation of the species at the northernmost extent of its breeding range in the Southern Ocean. The estimated number of births declined from a high (n = 38) in 1975 to a low (n = 2) in 2019, a 95% reduction at an average decrease of 2.15% per annum. The estimated mean time to extinction of this population from a linear regression model is 2 years (95% CI: 0–23 years). This decline is consistent with observed or forecasted population trends of some other marine top predators at the northern extent of their breeding ranges in the Southern Ocean; adding to the prevailing evidence that environmental change is the most plausible hypothesis explaining the range reduction of these marine species limited by a paucity of breeding grounds.

Accessible colonies of Grey-headed Albatross Thalassarche chrysostoma chicks on Marion Island have been inspected for chicks presenting mouse wounds from 2015, and during these inspections we found several cases of plumage and bill abnormalities. We report on two cases of leucism and three cases of ‘bent-beak syndrome’ in Grey-headed Albatross chicks, and one case of ‘bent-beak syndrome’ in a Light-mantled Albatross Phoebetria palpebrata chick. The leucistic Grey-headed Albatross chicks were found in 2018 and 2019, and both apparently fledged successfully. Three Grey-headed Albatross chicks with deviated upper mandibles were recorded in 2015, 2018 and 2019, and a single Light-mantled Albatross chick with deviated upper mandible was recorded in a study colony in 2014. None of these chicks survived to fledge. These appear to be the first records of leucism for Grey-headed Albatross, and the first records of bill deformities in any albatross species. Although bill deformities may have been overlooked in the past among Grey-headed and Light-mantled Albatrosses at Marion Island, it is worrying that we have had four records in the last few years. Albatrosses have been intensively studied at many colonies for more than 50 years, and we would have expected previous records of the ‘bent-beak syndrome’ if it occurred naturally at low levels, suggesting a novel threat to these seabirds.

Anomalous pelage colourations have been reported to occur in several pinniped species and can potentially be used to assess gene flow amongst conspecific populations. Aberrant pelage colour has not been documented in sub-Antarctic fur seals Arctocephalus tropicalis older than pups. Sub-Antarctic fur seals were inspected on two of the beaches at Gough Island, South Atlantic Ocean, in the austral summer of 2018/19. A leucistic adult male was sighted on 09 January 2019, the first recorded leucistic individual for the species. Given the apparent extreme rarity of leucism in this sub-Antarctic pinniped species, it is unlikely to contribute to assessment of gene flow amongst conspecific populations.