Cory's Shearwater, photograph by Paulo Catry

Jorge Pereira (Marine and Environmental Sciences Centre, University of Coimbra, Portugal) and colleagues have published in the journal Regional Environmental Change on foraging behaviour, body condition and breeding performance of Cory’s Shearwaters Calonectris borealis at two different breeding islands.

The paper’s abstract follows:

“Climate projections predict increases in the frequency and severity of extreme climate events over the next decades.  Hence, phases of extreme climatic indices are emerging as one of the most dangerous effects of climate chang though their impacts on wildlife populations are still poorly understood.  Here, we studied the foraging behaviour, body condition and breeding performance of a neritic (Berlenga Island) and oceanic (Corvo Island) population of Cory’s shearwaters (Calonectris borealis) in the mid-North Atlantic, during the two most positive and negative phases of North Atlantic Oscillation (NAO) reported in recent decades.  We showed that during an extreme negative NAO phase, birds from Berlenga spent less time foraging and provided less food to their chicks, which subsequently grew more slowly and were in poorer body condition. In contrast, the opposite pattern was found during the strong positive NAO phase in this population. Interestingly, during the same extreme negative NAO phase, birds from Corvo were more successful in terms of their foraging and breeding performance, taking advantage of the enhanced productivity associated with the cyclonic eddies (negative sea surface height anomalies) which occurred close to the colony. However, when anticyclonic eddies (positive sea surface height anomalies) were prevalent near the colony during the strong positive NAO phase, birds travelled longer distances, which negatively impacted their own body condition and that of their chicks.  Our study shows that populations breeding in neritic and oceanic areas of the eastern North Atlantic Ocean make contrasting foraging behavioural decisions in response to climate extremes and highlights the importance of mesoscale eddies for oceanic populations of pelagic seabirds.”

Reference:

Pereira, J.M., Paiva, V.H., Ceia, F.R. & Ramos, J.A. 2020.  Facing extremes: Cory’s shearwaters adjust their foraging behaviour differently in response to contrasting phases of North Atlantic Oscillation.  Regional Environmental Change 20.  doi.org/10.1007/s10113-020-01662-1.

John Cooper, ACAP Information Officer, 14 July 2020

Alexis Osborne checks a non-breeding Wandering Albatross for bands under permit on Marion Island, photograph by Peter Ryan

Alexis Osborne, recently awarded the degree of Master of Science for his study of moult in albatrosses and giant petrels, writes to ACAP Latest News:

“I started my journey to my first sub-Antarctic island in 2014 not knowing that this was going to be the start of big things.  As a young boy growing up in the arid Northern Cape Province of South Africa, I never dreamt of travelling at sea for days on end, let alone living on islands for a part of my life.  My first voyage was to Marion Island where I spent a year and where I also fell in love with seabirds.  I started collecting data while on Marion for an Honours project which I started upon my return to South Africa.  During 2017 I was fortunate to return to Marion Island, but also visited Gough Island and later that year Antarctica as well for their takeover periods. During my visit to Gough Island I knew immediately I wanted to stay for longer and when the opportunity presented itself in 2018 to return to Gough Island for a year, I grabbed it with both hands, not knowing I would be staying for two years.  I recently finished my degree of Master of Science in Biological Sciences at the University of Cape Town’s FitzPatrick Institute of African Ornithology.  I am currently still living on Gough Island and enjoying every moment but also looking forward to returning to South Africa.”

Photographing a Wanderer wing at Marion Island, photograph by Kim Stevens

The thesis abstract follows:

“Moult is an energetically demanding process for birds, and the replacement of flight feathers impacts flight performance.   As a result, few birds overlap moult with other key activities such as breeding or migrating.  Feather growth rates show little change in relation to body size, so large birds with long flight feathers take a long time to grow individual feathers, making their moult even more challenging.  Unless these birds can afford to become flightless for several weeks while they replace all their flight feathers simultaneously, many large birds lack sufficient time to breed and replace all their wing feathers each year.  As a result, they have evolved complex moult strategies that replace a subset of feathers each year.  Albatrosses and giant petrels are prime examples of birds facing this challenge.  This study focusses on Wandering Albatrosses (Diomedea exulans) and Northern Giant Petrels (Macronectes halli) breeding at Marion Island and Southern Giant Petrels (M. giganteus) at Gough Island.  I explore primary and secondary moult patterns in Wandering Albatrosses and secondary and greater secondary coverts in giant petrels in relation to breeding activity.

I used digital photography to record the wear patterns in the wings of Wandering Albatrosses and giant petrels. Using photographs of upperwings of marked individuals over time allowed the opportunity to track changes in the wear pattern among specific feathers, although scoring feather wear from images works better for darker feathers. The rate of wear among secondaries and their coverts differed across the wing, with the inner feathers wearing faster than the central feathers. Photographing the extended wings of albatrosses and petrels incubating eggs had no impact on hatching success. Using this method I was able to test the often held assumption that wing feather moult is largely symmetrical. In Wandering Albatrosses, moult symmetry was greatest in outer flight feathers, especially primaries. However, the pattern of increasing asymmetry towards the body was not consistent; inner primaries showed less symmetry than outer secondaries and inner secondaries were moulted with greater symmetry than central secondaries. Giant petrels preferentially replaced the inner and outer secondaries and the inner and outer greater secondary coverts, and feather symmetry was greatest in these feathers. All three species indicated some asymmetry in all feathers that had an incomplete annual moult. Depending on the question being asked, I recommend scoring both wings when investigating moult patterns.

Wandering Albatrosses typically take a sabbatical year following a successful breeding attempt, and thus failed breeders usually have less time to moult between successive breeding attempts. Following a successful breeding attempt, Wandering Albatrosses from Marion Island replaced a similar number of primary feathers on average (males 7.9 and females 7.3) as birds from the Crozet Islands (males 8.8 and females 8.1) and South Georgia (males 8.6 and females 7.1). Wandering Albatrosses that do not skip a year following a failed breeding attempt, not only replaced fewer feathers on average, but showed a difference in number of feathers replaced between sexes at Marion Island (males 7.4, females 6.1), as previously reported at the Crozet Islands (males 8.3, females 6.5) and South Georgia (males 7.2, females 5.2). These results suggest that females are under greatest pressure when a breeding attempt fails. Because females from South Georgia replace fewer feathers, especially following a failed breeding attempt, they might be under more stress than females from populations breeding at islands in the Indian Ocean (Marion and Crozet). This parallels the contrasting population trends in these regions, with numbers increasing over the last few decades in the Indian Ocean (Marion and Crozet Islands) but decreasing steadily at South Georgia. General Linear Models (GLMs) showed that sex and time available to moult both influenced the number and mass of flight feathers replaced. Sex explained more variation in terms of number of feathers replaced (67%) than time available to moult (33%), but time available to moult explained 68% of the mass of flight feathers replaced. However, there is large variation among birds in the number of primaries and secodaries replaced, independent of time available for moult. Together, sex and time available to moult accounted for only 9.2% (number) and 11.9% (mass) of the variance in feathers replaced.

Giant petrels are one of the largest birds that undergo a complete primary moult each year without losing the ability to fly. They do this by overlapping their moult with breeding and by moulting several primaries at once. Being annual breeders, individuals that fail a breeding attempt have more time to moult than successful breeders, and therefore replaced more flight feathers. Northern Giant Petrels having a successful breeding attempt replaced on average the same percentage of secondary and greater secondary coverts in both sexes; Following a successful breeding attempt Southern Giant Petrels (both sexes) replaced more feathers (secondaries and greater secondary coverts) than Northern Giant Petrels. I found that in a failed breeding attempt giant petrels have more time to moult and therefore replaced more secondary feathers than successful breeders. GLMs showed that breeding outcome was the only variable that influenced the mass of feathers replaced in Northern Giant Petrels, accounting for 14% of the variance in feathers replaced, while sex was the only variable in Southern Giant Petrels, accounting for 6% of variance. When both species were modelled together with sex and breeding attempt as explanatory variales, only breeding attempt was significant, accounting for 11% of the variance in the mass of secondaries and coverts replaced.

In summary, the assumption that breeding activity, and thus the time between breeding attempts, influences the extent of moult in large birds with incomplete wing moults was supported for Wandering Albatrosses and Northern Giant Petrels. However, time available for moult explained only a small proportion of individual variation in moult extent in these species. Southern Giant Petrels replaced a similar mass of flight feathers, irrespective of breeding outcome. My results suggest that factors other than time between breeding attempts are important in determining the extent of wing moult.

My study highlights the important tradeoffs large birds are required to make when balancing moult and reproduction. Annual monitoring of moult patterns in known individuals provides a valuable tool to better understand moult patterns in these large, long-lived birds.”

A Southern Giant Petrel on its nest on Gough Island, photograph by Peter Ryan

With thanks to Alexis Osborne.

Reference:

Osborne, A. 2020.  Understanding Moult Patterns in Albatrosses and Petrels breeding on Marion and Gough Islands.  MSc thesis. Department of Biological Sciences, University of Cape Town. 82 pp.

NOTE:  the thesis will be available online after Alexis officially graduates later this year.

John Cooper, ACAP Information Officer, 13 July 2020

Releasing the Northern Giant Petrel

A Northern Giant Petrel Macronectes halli was rescued and brought to the Wildlife Hospital, Dunedin in New Zealand by the Department of Conservation in Invercargill last month.  The bird described as “weak and underweight on arrival” had an old fracture on its left wing that had started healing “a bit skew”.  From its dark-brown plumage it is possibly a juvenile although its outstretched wing shows primary moult occurring.  Following X-rays by the hospital’s vets the wildlife hospital reported:

“The fracture to the wing is not too badly displaced and has started to heal pretty well. It is not perfectly straight although he seems to use the wing very well.  Our vet team have weighed up the pros and cons of performing surgery to straighten the bone or leave him be. Surgery of course always comes with risks because of anaesthesia.  In this case we would need to pluck feathers, re-fracture the bone and pin it to straighten it.  All of this would extend his hospital stay by months.  The team have decided that the cons of prolonged hospitalization and the risk of surgery far outweigh releasing him with a slightly crooked wing that is unlikely to have much impact on his ability to fly.  Large seabirds are also at risk of contracting aspergillosis when in a hospital situation and pododermatitis (bumblefoot/pressure sores) from being on land so long.”

Following being colour-banded, the bird was released from a sandy beach on 7 July - from where it swam out to sea.

On the beach after release

Watch video clips of the giant petrel being fed fish and swimming in a rehabilitation pool on the Hospital’s Facebook page.

The hospital is a veterinary facility specialising exclusively in the treatment of New Zealand’s native species.

UPDATE: Following an enquiry, the hospital has confirmed that the bird was seen flying after release.

John Cooper, ACAP Information Officer, 10 July 2020, updated 11 July 2020

Julie McInnes (Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia) will give an on-line lecture entitled "The use of DNA-based diet analysis of higher-order predators as a conservation management tool: assessing fishery interactions, food-web linkages and ecosystem changes" via Zoom on 14 July.  Julie holds an RJL Hawke Fellowship in Antarctic Science.

A description of her seminar follows:

“A key component of ecosystem monitoring programs that aim to support the maintenance of biodiversity and ecosystem function is sound knowledge of species composition and food web linkages. This information provides a foundation for assessing ecosystem changes and can allow causal links to be clarified (e.g. interactions between marine predators and fishery resources). Seals and seabirds are responsive and reflective of changes in the availability of lower trophic levels, which makes these predators ideal indicator species for changes in marine ecosystems. Dietary studies provide a mechanism to assess environmental and fisheries-related changes in marine systems, as well as the marine biodiversity of a region.  DNA metabarcoding of predator scats is a non-invasive tool which allows the diet of a range of predator species to be investigated simultaneously, increasing our understanding of ecosystem connectivity and food web structure.  This seminar will highlight the value of DNA diet analysis in conservation and management, including the assessment of seabird-fishery interactions in Tasmania, and provide an overview of the RJL Hawke Antarctic Fellowship.  During this fellowship we will develop a marine ecosystem monitoring framework using top predator scat DNA to assess species biodiversity in the Subantarctic.  By simultaneously studying the diet of a range of predators, we will resolve food web linkages and investigate the use of quantitative models integrating DNA sequence datasets. Through the collation of existing dietary data and new robust dietary information, we will provide a sound foundation for future monitoring programs to assess changes in species diversity and identify species that may be at risk from fishery engagement.”

Join the Zoom seminar on ID: 989 6500 4574; 13h00 Australian Eastern Standard Time (AEST).

John Cooper, ACAP Information Officer, 09 July 2020