Sexual and individual foraging segregation in Gentoo penguins Pygoscelis papua from the Southern Ocean during an abnormal winter

Knowledge about sexual segregation and gender-specific, or indeed individual specialization, in marine organisms has improved considerably in the past decade. In this context, we tested the “Intersexual Competition Hypothesis” for penguins by investigating the feeding ecology of Gentoo penguins during their austral winter non-breeding season. We considered this during unusual environmental conditions (i.e. the year 2009 had observations of high sea surface and air temperatures) in comparison with the long term average at Bird Island, South Georgia. Through conventional (i.e. stomach contents) and stable isotopic values from red blood cells, plasma and feathers of both male and female Gentoo penguins, we showed that there were significant differences between sexes, with males feeding mainly on fish (54% by mass) followed by crustaceans (38%) whereas females fed mainly on crustaceans (89% by mass) followed by fish (4%). Themisto gaudichaudii was the most important crustacean prey for males (64% by mass; 82% by number; 53% by frequency of occurrence) and females (63% by mass; 77% by number; 89% by frequency of occurrence), contrasting with all previous studies that found Antarctic krill Euphausia superba were generally the main prey. Stable isotopic data showed that, in terms of habitat use (based on δ 13C), there were significant differences in short-term carbon signatures between males and females (based on plasma and red blood cells), suggesting that both sexes explored different habitats, with females exploring more offshore pelagic waters and males feeding more in coastal benthic waters. Based on δ 15N, males fed on significantly higher trophic level than females (based on plasma and red blood cells), in agreement with our diet results., Thus, Gentoo penguins behave in a similar manner to other non-breeding penguins species (e.g. king, macaroni and rockhopper penguins), albeit at a smaller spatial scale (as they do not disperse as these other penguins do), in that they have a wider habitat and trophic niche during the Antarctic Winter (in comparison to Summer). We also detected individual specialization in feeding/trophic levels for each gender, with certain males feeding mainly on fish and certain females mainly on crustaceans, which may be driven the prevailing environmental conditions that lead individuals to search for alternative prey, and cause sexual diet segregation. Our results provide further information to help improve understanding about sexual segregation and individual specialization of marine organisms, while contributing valuable information on the winter diet for Antarctic monitoring programs and for modelling Antarctic marine food webs

Effects of competitive pressure and habitat heterogeneity on niche partitioning between Arctic and boreal congeners

The rapidly changing climate in the Arctic is expected to have a major impact on the foraging ecology of seabirds, owing to changes in the distribution and abundance of their prey but also that of competitors (e.g. southerly species expanding their range into the Arctic). Species can respond to interspecific competition by segregating along different niche axes. Here, we studied spatial, temporal and habitat segregation between two closely related seabird species: common guillemot Uria aalge (a temperate species) and Brünnich’s guillemot Uria lomvia (a true Arctic species), at two sympatric sites in Iceland that differ in their total population sizes and the availability of marine habitats. We deployed GPS and temperature-depth recorders to describe foraging locations and behaviour of incubating and chick-rearing adults. We found similar evidence of spatial segregation at the two sites (i.e. independent of population sizes), although segregation in environmental space was only evident at the site with a strong habitat gradient. Unexpectedly, temporal (and, to a limited extent, vertical) segregation appeared only at the least populated site. Overall, our results show complex relationships between the levels of inferred competition and that of segregation

Cold comfort: Arctic seabirds find refugia from climate change and potential competition in marginal ice zones and fjords

Climate change alters species distributions by shifting their fundamental niche in space through time. Such effects may be exacerbated by increased inter-specific competition if climate alters species dominance where competitor ranges overlap. This study used census data, telemetry and stable isotopes to examine the population and foraging ecology of a pair of Arctic and temperate congeners across an extensive zone of sympatry in Iceland, where sea temperatures varied substantially. The abundance of Arctic Brünnich’s guillemot Uria lomvia declined with sea temperature. Accessibility of refugia in cold water currents or fjords helped support higher numbers and reduce rates of population decline. Competition with temperate Common guillemots Uria aalge did not affect abundance, but similarities in foraging ecology were sufficient to cause competition when resources are limiting. Continued warming is likely to lead to further declines of Brünnich’s guillemot, with implications for conservation status and ecosystem services

Analisis Rasio Likuiditas, Aktivitas, dan Profitabilitas terhadap Return Saham Perusahaan Wholesale yang Terdaftar di Bursa Efek Indonesia

Globalisasi mengakibatkan perkembangan Perusahaan di dunia sangat pesat, sehingga menimbulkan persaingan antar Perusahaan sejenis yang sangat ketat. Perusahaan dihadapkan dengan adanya masalah produktivitas yang tinggi, sehingga dapat memenuhi permintaan konsumennya, selain masalah produktivitas yang tinggi tentunya Perusahaan juga harus memperhatikan tingkat atau harga saham yang ada pada Perusahaan, dengan begitu tujuan Perusahaan bisa tercapai. Penelitian ini bertujuan untuk mengetahui pengaruh rasio likuiditas (current ratio), rasio aktivitas (assets turn over), dan rasio profitabilitas (return on equity) terhadap return saham pada Perusahaan Wholesale (Durable & Non Durable Goods). Metode yang digunakan adalah asosiatif.Populasi penelitian berjumlah 32 Perusahaan dengan teknik pengambilan sampel purposive sampling dan dari 32 Perusahaan diambil 10 Perusahaan yang memenuhi kriteria.Hasil penelitian menunjukanreturn on equity berpengaruh positif dan signifikan terhadap return saham, sementara current ratio dan assets turnover berpengaruh negatif terhadap return saham.sebaiknya manajemen Perusahaan memperhatikan aspek likuiditas dan perputaran aset sehingga peningkatan kinerja dari kedua variabel tersebut akan meningkatkan return saham Perusahaan. Kata kunci:current rasio, assets turn over, return on equity

Population size and decadal trends of three penguin species nesting at Signy Island, South Orkney Islands

We report long-term changes in population size of three species of sympatrically breeding pygoscelid penguins: Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarctica) and gentoo (Pygoscelis papua ellsworthii) over a 38 year period at Signy Island, South Orkney Islands, based on annual counts from selected colonies and decadal all-island systematic counts of occupied nests. Comparing total numbers of breeding pairs over the whole island from 1978/79 to 2015/16 revealed varying fortunes: gentoo penguin pairs increased by 255%, (3.5% per annum), chinstrap penguins declined by 68% (-3.6% per annum) and Adélie penguins declined by 42% (-1.5% per annum). The chinstrap population has declined steadily over the last four decades. In contrast, Adélie and gentoo penguins have experienced phases of population increase and decline. Annual surveys of selected chinstrap and Adélie colonies produced similar trends from those revealed by island-wide surveys, allowing total island population trends to be inferred relatively well. However, while the annual colony counts of chinstrap and Adélie penguins showed a trend consistent in direction with the results from all-island surveys, the magnitude of estimated population change was markedly different between colony wide and all island counts. Annual population patterns suggest that pair numbers in the study areas partly reflect immigration and emigration of nesting birds between different parts of the island. Breeding success for all three species remained broadly stable over time in the annually monitored colonies. Breeding success rates in gentoo and chinstrap penguins were strongly correlated, despite the differing trends in population size. This study shows the importance of effective, standardised monitoring to accurately determine long-term population trajectories. Our results indicate significant declines in the Adélie and chinstrap penguin populations at Signy Island over the last five decades, and a gradual increase in gentoo breeding pairs

Long-term population size and trends of South Georgia Shags (Leucocarbo [atriceps] georgianus) at Signy Island, South Orkney Islands and Bird Island, South Georgia

The South Georgia Shag Leucocarbo [atriceps] georgianus has breeding populations on the islands of South Georgia, the South Sandwich and South Orkney Islands. The South Orkney Islands are estimated to support ~ 18%–37% of the global population and South Georgia a further 37%–69%. Here, we examine changes in South Georgia Shag population size and productivity from Signy Island, South Orkney Islands, over a 43 year period (1978/1979 to 2020/2021) and from Bird Island, South Georgia, over a 32 year period (1989/1990 to 2020/2021). Analysis of total nesting pairs at Signy Island revealed an overall decline of 40.9% (− 1.3% per annum), with an increase during the 1980s, followed by a fluctuating decline from the 1990s to 2020/2021. Although the two Signy Island colonies showed correlated fluctuations in numbers of nesting pairs, over the whole time period these colonies showed markedly different population trajectories, indicating the limitations of using part-island counts to infer whole island trends, particularly given the low breeding-site fidelity in this species. Nest occupation in the larger colony (596 nests in 1978/1979) declined by 77.2% (− 3.5% per annum) whilst the smaller colony (50 nests in 1978/1979) exhibited an increase of 492% (+ 3.8% per annum). A decline in occupied nests of 58.3%, (− 2.8% per annum), has occurred in the Bird Island population since 1989/1990. Continuation of the significant decline in breeding numbers revealed in this study may be of important conservation concern, particularly as this trend has been mirrored at another site within the South Orkneys

A juvenile Tristan albatross (Diomedea dabbenena) on land at the Crozet Islands

Abstract: Albatrosses and other seabirds are generally highly philopatric, returning to natal colonies when they achieve breeding age. This is not universal, however, and cases of extraordinary vagrancy are rare. The Tristan Albatross (Diomedea dabbenena) breeds on Gough Island in the South Atlantic Ocean, with a small population on Inaccessible Island, Tristan da Cunha, ca 380 km away. In 2015, we observed an adult male albatross in Gonydale, Gough Island, which had been ringed on Ile de la Possession, Crozet Islands in 2009 when it was assumed to be an immature Wandering Albatross (D. exulans). We sequenced 1109 bp of the cytochrome b mitochondrial gene from this bird, and confirmed it to be a Tristan Albatross, meaning its presence on Crozet 6 years previous, and nearly 5000 km away, was a case of prospecting behaviour in a heterospecific colony. Given the challenges in identifying immature Diomedea albatrosses, such dispersal events may be more common than thought previously.This is an open access article, available to all readers online, published under a creative commons licensing (https://creativecommons.org/licenses/by/4.0/)

Location of South Orkney Islands, and distribution of penguin study colonies on Signy Island.

<p>Legend: A = Adélie, C = chinstrap and G = gentoo.</p

Annual penguin breeding success from 1978/79-2015/16 on Signy Island.

<p>Legend: the proportion of chicks fledged by breeding pairs (breeding productivity) from (a) Adélie, (b) chinstrap and (c) gentoo colonies. Note this data includes the entire island gentoo penguin population. Smooth trends (dashed lines) are plotted using least squares fitting of a first order polynomial for each species.</p

Pairs of Adélie, chinstrap and gentoo penguins counted at Signy Island and offshore islands, 1947/48–2015/16.

<p>Pairs of Adélie, chinstrap and gentoo penguins counted at Signy Island and offshore islands, 1947/48–2015/16.</p