A breeding Grey-headed Albatross on Marion Island carries a back-mounted GPS logger, photograph by Kim Stevens

Tegan Carpenter‐Kling (Marine Apex Predator Research Unit, Nelson Mandela University, Port Elizabeth, South Africa) and colleagues have published open access in the journal Ecology and Evolution on aspects the foraging behaviour of four sub‐Antarctic albatross species.

The paper’s abstract follows:

“Seasonal and annual climate variations are linked to fluctuations in the abundance and distribution of resources, posing a significant challenge to animals that need to adjust their foraging behavior accordingly.  Particularly during adverse conditions, and while energetically constrained when breeding, animals ideally need to be flexible in their foraging behavior.  Such behavioral plasticity may separate “winners” from “losers” in light of rapid environmental changes due to climate change.  Here, the foraging behavior of four sub‐Antarctic albatross species was investigated from 2015/16 to 2017/18, a period characterized by pronounced environmental variability.  Over three breeding seasons on Marion Island, Prince Edward Archipelago, incubating wandering (WA, Diomedea exulans; n = 45), grey‐headed (GHA, Thalassarche chrysostoma; n = 26), sooty (SA, Phoebetria fusca; n = 23), and light‐mantled (LMSA, P. palpebrata; n = 22) albatrosses were tracked with GPS loggers.  The response of birds to environmental variability was investigated by quantifying interannual changes in their foraging behavior along two axes: spatial distribution, using kernel density analysis, and foraging habitat preference, using generalized additive mixed models and Bayesian mixed models. All four species were shown to respond behaviorally to environmental variability, but with substantial differences in their foraging strategies. WA was most general in its habitat use defined by sea surface height, eddy kinetic energy, wind speed, ocean floor slope, and sea‐level anomaly, with individuals foraging in a range of habitats. In contrast, the three smaller albatrosses exploited two main foraging habitats, with habitat use varying between years. Generalist habitat use by WA and interannually variable use of habitats by GHA, SA, and LMSA would likely offer these species some resilience to predicted changes in climate such as warming seas and strengthening of westerly winds. However, future investigations need to consider other life‐history stages coupled with demographic studies, to better understand the link between behavioral plasticity and population responses.”

Reference:

Carpenter‐Kling, T., Reisinger, R.R., Orgeret, F., Connan, M., Stevens, K.L., Ryan, P.G., Makhado, A. & Pistorius, P.A. 2020.  Foraging in a dynamic environment: response of four sympatric sub‐Antarctic albatross species to interannual environmental variability.  Ecology and Evolution doi.org/10.1002/ece3.6766.

John Cooper, ACAP Information Officer, 30 September 2020

  The bird-scaring kite deployed, photograph by Emanuel Constantino

Nuno Oliveira (Sociedade Portuguesa para o Estudo das Aves – SPEA, Lisbon, Portugal) and colleagues have published in the journal Bird Conservation International showing that a "raptor-like" bird-scaring kite reduced the chances of seabird bycatch by purse seiners.

The paper’s abstract follows:

“Bycatch is one of the main threats to marine biodiversity, affecting ocean ecosystems at a worldwide scale.  The main focus of bycatch studies has been on the impact of larger vessels, with few studies assessing the impact of artisanal fisheries.  Moreover, bycatch studies are often limited to a small number of marine regions, and significant gaps still exist in our knowledge of the spatial and temporal patterns of seabird bycatch.  Here we present a multi-approach method to accurately quantify seabird bycatch driven by small- and medium-sized fishing fleets operating in a high priority area for seabird conservation on the Portuguese mainland.  Results of three mitigation measures to reduce seabird bycatch on fishing gear where seabird bycatch is most likely to occur were also tested: high contrast panels in bottom gillnets, black hooks in demersal longlines and a bird scaring device in purse seines.  The efficacy, acceptance, and economic viability were tested for each mitigation measure.  Sixty-seven individuals of seven seabird species were bycaught during 295 monitored fishing trips between 2015 and 2018.  Bycatch occurred mainly in demersal longlines (0.07 birds fishing event-1), followed by purse seines (0.02 birds fishing event-1) and bottom gillnets (0.01 birds fishing event-1).  Nevertheless, the bird scaring device caused birds to interact less with the vessel (the presence of gulls was reduced by 11%), thus decreasing the likelihood of bycatch.  This device has proved to be low-cost (representing less than 5% income of a single day’s landings) and easy to implement, being also well accepted by purse seine fishermen.  It was not possible to evaluate the efficacy of high contrast panels and black hooks, as no bycatch events were recorded during trials.”

A drowned Cory's Shearwater Calonectris borealis comes aboard on a Portuguese longline, photograph by Iván Gutiérrez

Read a related post here.

With thanks to Nuno Oliveira.

Reference:

Oliveira, N., Almeida, A., Alonso, H., Constantino, E., Ferreira, A., Gutiérrez, I., Santos, A., Silva, E. & Andrade, J. 2020.  A contribution to reducing bycatch in a high priority area for seabird conservation in Portugal. Bird Conservation International, 1-20. doi:10.1017/S0959270920000489.

John Cooper, ACAP Information Officer, 29 September 2020

Great Shearwater at sea

Paloma Carvalho (Department of Biological Sciences, University of Manitoba, Winnipeg, Canada) and colleagues have published open access in the journal Marine Ornithology on foraging behaviour of Great Shearwaters gravis and Sooty A. grisea Shearwaters off Newfoundland.

The paper’s abstract follows:

“Species tend to concentrate in areas with high prey availability, which could lead to competitive interactions within a feeding assemblage as resources become depleted. In coastal Newfoundland, Canada, capelin Mallotus villosus is the focal forage fish species that many top predators feed on during the summer; however, inshore availability varies throughout the boreal summer when abundant aggregations migrate inshore to spawn. We investigated the interactions and responses of Great Shearwaters Ardenna gravis and Sooty Shearwaters A. grisea during their non-breeding season to supplemental food supply under changing natural prey availability (higher and lower capelin availability) by conducting an at-sea experiment during July-August (2015/2016) in coastal Newfoundland. Supplemental food was offered every 30 s over 10 min (‘experimental period'), which was preceded and followed by 10-min control periods (i.e., no food provided). The number of both species increased during the experimental periods, indicating that both species were attracted to the food supplementation experiment. Great Shearwaters were 7.6-13.8 times more likely than Sooty Shearwaters to land near the experimental platform and 95.2 times more likely than Sooty Shearwaters to fight over supplemental food items with individuals of the same or different species. These species-specific tendencies remained consistent as prey availability varied within years, but both species increased in their abundance and interactions with other species (including Herring Gulls Larus argentatus and Northern Fulmars Fulmarus glacialis) during prey capture at lower relative to higher prey availability, as evidenced by lower proportions of flying birds and a greater likelihood of landing on the water. Overall, we suggest that when Great and Sooty shearwaters feed in close association, Great Shearwaters are the more competitively dominant species, which may lead to higher risks of by-catch mortality, especially when the availability of natural prey decreases.”

Reference:

Carvalho, P.C., Maynard, L.D. & Davoren, G.K. 2020. Responses of sympatric shearwaters to supplemental food under varying natural prey availability on the wintering grounds of coastal Newfoundland, Canada. Marine Ornithology 48: 255-262.

John Cooper, ACAP Information Officer, 28 September 2020

UPDATED  The new team is now ashore on Gough Island

From left: Alexis Osborne, Chris Jones, Kim Stevens, Michelle Risi, Vonica Perold and Roelf Daling meet up at Gough's helipad; photograph from FitzPsatrickn Institute of Ornithology

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Ready to depart: Gough Island Restoration Programme members on the helideck of the S.A. Agulhas II in Cape Town's harbour
From left: Richard Hall, Vonica Perold, Roelf Daling, Kim Stevens & Nini van der Merwe

The annual relief voyage to Gough Island departed from Cape Town on 19 September under strict COVID-19 health protocols to maintain the long-term meteorological record by the South African Weather Service (SAWS) and seabird monitoring by the UK’s Gough Island Restoration Programme (GIRP) that aims to eradicate the island’s introduced House Mice.  All members of the overwintering team (G66) were quarantined for 10 days and then tested for the virus before departure in an approved quarantine facility in accordance with South African Department of Health requirements (click here).

Five GIRP members are aboard South Africa’s Antarctic research and supply vessel the S.A. Agulhas II.  Three of the programme staff will stay on Gough Island for the next year, taking over from the current field team (Chris Jones, Alexis Osborne and Michelle Risi) who have spent two years on the island.  Kim Stevens, Vonica Perold and Roelf Daling will continue the long-term monitoring of seabirds (including the Critically Endangered Tristan Albatross Diomedea dabbenena) on the island (click here).  Six months after having made the decision to postpone the 2020 mouse eradication, GIRP is now working towards making an attempt in 2021, although it reports that the increase in project costs will be substantial with the need for new contracts for personnel, vessels, helicopters and insurance.

At risk to mice: a Tristan Albatross guards its chick in a monitoring colony on Gough Island, photograph by Michelle Risi

The S.A. Agulhas II is expected to return to Cape Town on 16 October.  The Gough sailing comes just two days after a field team sailed from Cape Town for South Africa’s other sub-Antarctic base to restart monitoring of albatrosses on Marion Island placed on hold due to COVID-19 (click here).

With thanks to Laura Beasley, Nini van der Merwe, Michelle Risi and Kim Stevens.

John Cooper, ACAP Information Officer, 23 September 2020

Postscript: no COVID-19 masks will be needed on Gough Island!