Conserving Benguela endemic seabirds
All three seabirds endemic to the Benguela upwelling ecosystem that rely on anchovies and sardines are threatened by local reductions in the availability of their preferred prey. Small pelagic fish abundance has decreased off the southern African west coast, where fishing effort is concentrated and most seabird breeding islands are located. As a result, it is crucial to understand the foraging behaviour of breeding seabirds and how their populations respond to changes in fish abundance and distribution.
Recent studies indicate that the South African sardine population comprises two stocks, one off the west coast and one off the south coast. The lack of spatial management of the fishery has resulted in over-exploitation of the west coast stock. In 2018, the sardine fishing industry was closed for three months in an attempt to alleviate the pressure on the stock, but conditions for African Penguins Spheniscus demersus, Cape Gannets Morus capensis and Cape Cormorants Phalacrocorax capensis breeding at west coast location remain poor. However, not all seabirds in the region are decreasing. Greater Crested (or Swift) Tern Thalasseus bergii numbers have increased over the last few decades, despite feeding on the same small pelagic fish prey as the three endemic species. Understanding the drivers behind these population changes is the crucial first step necessary to mitigating population declines. This is a large, multi-faceted programme with key participants including Pierre Pistorius, Lorien Pichegru and Maëlle Connan (NMU), David Grémillet (CNRS Montpellier), former post-docs Tim Cook (Paris) and Richard Sherley (Bristol), collaborators at BLSA (Ross Wanless, Christina Hagen) and DEA (Azwianewi Makhado and Rob Crawford), as well as several post-doctoral students..
Activities in 2018
- After completing his PhD at the Fitz, Alistair McInnes has held a CoE post-doctoral position at NMU studying the use of seabirds as real-time monitors of pelagic fish availability. Working mainly at Stony Point, Betty’s Bay, home to the only increasing population of African Penguins, he continues to use cameras and GPS loggers and locally-designed weigh-bridges to measure how hard penguins have to work to catch prey.
- NMU postdoc, Dr Giannina Passuni, mentored by Lorien Pichegru and NMU’s Nadine Strydom, has been investigating the stomach contents ofanchovies eaten by African Penguins to understand the diet of the penguins’ main prey. These data will be analysed together with acoustic estimates of the abundance and distribution of small pelagic fish and the foraging areas of tracked penguins. Working with SAEON’s Algoa Bay node, she also sampled nutrient concentrations and plankton diversity and biomass around St Croix Island eight times over a year to evaluate the influence of nutrient inputs from the largest African Penguin colony on the feeding environment for larval anchovy and sardine. Her ultimate aim is to understand how changing environmental conditions will affect top predators.
- The experimental closure of commercial fishing for small pelagic fish around key penguin breeding islands continued in 2018, with the waters around St Croix Island once again opened to fishing, after three years of closure. This corresponded with a marked increase in penguin foraging distances, confirming the significant benefit of fishing exclusions around penguin colonies, especially when fish are scarce. The results of the experiment taking place in Algoa Bay from 2008 to 2018 will be published in 2019. Determining a threshold below which fishing exclusions should be implemented to benefit penguins could be integrated in a Dynamic Ocean Management plan that allows fishing to occur around colonies when fish abundance is high, thereby reducing the cost to the fishery.
- NMU PhD student Gwendoline Traisnel published a paper on African Penguin ‘personalities’ in Ethology and investigated if these traits influenced foraging behaviour. Her resultant paper, currently in press with Ibis, shows that resource acquisition strategies are linked to personality types only in female African penguins. Bolder females follow a moresinuous foraging path than shy birds, and dive more extensively. Gwendoline also investigated if consistency in foraging strategies could relate to personalities and benefit breeding success. Her paper in Marine Ecological Progress Series showed that females exhibit greater foraging flexibility than males, possibly adapting to their brood’s needs. When environmental conditions were poor, parents with consistent, repeatable foraging strategies had higher breeding success, presumably because regular feeding events favoured chick growth.
- Gwendoline also published a note in Marine Ornithology showing how a heat wave early in the breeding season led to the mass abandonment of a large part of the Bird Island colony of African Penguins. When these birds returned for a second breeding attempt later in the season, they killed some chicks from earlier breeding attempts, in an unanticipated impact of climate change.
- NMU PhD student Katharina Reusch completed a second field season on the foraging ecology of Kelp Gulls Larus dominicanus. She deployed GPS loggers and collected stomach and blood samples from incubating Kelp Gulls from colonies varying in their access to human-produced food. Her preliminary findings reveal a wide variety of food items, independent of the distance to towns or refuse dumps. She has processed >600 blood samples from adults for stable isotopes to compare the signatures across seven study colonies.
- Lorien Pichegru mentored two Honours students in the Department of Mechatronics at NMU who designed a heart-rate recorder and a GPS/depth recorder for African Penguins.
- Pierre Pistorius continued monitoring Cape Gannets at Bird Island in Algoa Bay, and collected further tracking and demographic data from this colony. Jonathan Botha, a former MSc student on this project, demonstrated interesting differences in foraging behaviour during the guard and post-guard phases in Frontiers in Marine Science. Gavin Rishworth, another former MSc student, also published a paper on the VHF-based monitoring of Cape Gannets in the Journal of Marine Systems showing the relative importance of sex, offspring age and weather conditions on the time that adult gannets spend at sea while provisioning their offspring. Post-doc Andrea Thiebault used tracking data from these birds, in conjunction with data from small video-cameras deployed on the birds, to derive new methods for identifying seabird behaviours at sea. She also continued her research into acoustic communication in gannets.
- NMU Post-doc Ralph Vanstreels had a productive year applying his veterinary skills in studying health and conservation aspects relevant to seabirds. Danielle van den Heever, under the supervision of Pierre Pistorius at NMU, completed her MSc on the at-sea habitat use by Wedge-tailed Shearwaters Ardenna pacifica breeding at Reunion and the Seychelles.
- Ilana Engelbrecht continued working on her MSc with Pierre Pistorius on foraging strategies and within-pair synchronization in Cape Gannets at Bird Island. The project is based on the extensive set of foraging trip durations of individuals tagged with VHF transponders.
- David Grémillet and Lorien Pichegru attempted to continue their long-term study tracking the foraging ranges of Cape Gannets breeding on Malgas Island, which was initiated in 2002. The intention was to deploy GPS on individuals of known-age to explore how experience influences foraging success. However, breeding on Malgas Island was greatly delayed in 2018, with very few birds in the colony, probably as a result of predation by Cape fur seals within the colony. More than 1000 gannet eggs also were found to be predated by Kelp Gulls, many more than usual, possibly as a consequence of the disturbance by seals.
- Former PhD student Davide Gaglio, who graduated in 2017, published four more papers on Greater Crested Tern foraging ecology and diet, and was instrumental in a paper estimating the tern’s survival rate led by visiting post-doc Ana Payo-Payo.
- MSc student Laurie Johnson finished writing up her MSc, co-supervised by Maëlle Connan and Peter Ryan. In it, she tests the assumption that stable isotope signals in feathers remain constant, and uses stable isotopes to study the diets of predators in the Namibian Islands Marine Protected Area.
- Emmanuel Adekola arrived from Nigeria to start a PhD on moult in birds, with a focus on Cape Gannets.
- MSc students Danielle van den Heever (NMU) and Oyena Masiko (CB UCT) graduated in 2018. Danielle obtained a distinction for her thesis on Wedge-tailed Shearwater foraging ecology.
- Peter Ryan gave a plenary talk at the 29th IOC in Vancouver on seabird conservation from a Southern Hemisphere perspective, drawing on work from this programme and the Southern Ocean programme.
- Lorien Pichegru was lead editor of a popular book, Amazing Features and Creatures of Algoa Bay, that highlights the diversity of marine species and habitats in Algoa Bay.
- .Lorien also attended the 5th International Marine Conservation Congress in Kutching, Malaysia, where she gave a talk on the benefits of fishery exclusion zones to African Penguins. The presentation will be published in Frontiers in Marine Science.
- Ex-CoE student, Gavin Rishworth, published a synthesis of his MSc work on time-activity budgets in Cape gannets in the Journal of Marine Systems.
- Ralph Vanstreels identified a novel candidate species of Anasplasma, a bacterium transmitted by ticks, in the erythrocytes of African Penguins. This is the first time this genus has been identified in birds, and was published in Parasites and Vectors.
BirdLife International; BirdLife South Africa; DST-NRF CoE grant; Raggycharters Whale Watching.
Dr Pierre Pistorius (NMU)
Prof. Res Altwegg (SEEC, UCT)
Prof. Peter Ryan (FIAO, UCT)
Dr Lorien Pichegru (NMU)
Dr Maëlle Connan (NMU)
Dr Timotheé Cook (U. Paris)
Dr Rob Crawford (Oceans & Coasts, DEA)
Dr Jon Green (U. Liverpool)
Dr David Grémillet (FIAO, UCT and CNRS)
Dr Azwianewi Makhado (Oceans & Coasts, DEA)
Dr Alistair McInnes (NMU Post-doc)
Dr Florian Orgeret (NMU Post-doc)
Dr Giannina Passuni (NMU Post-doc)
Dr Richard Sherley (U. Bristol)
Dr Andrea Theibault (NMU Post-doc)
Dr Ralph Vanstreels (NMU Post-doc)
Dr Ross Wanless (FIAO, UCT and BLSA)
Students: Emmanuel Adekola (PhD, UCT), Katharina Reusch (PhD, NMU), Gwendoline Traisnel (PhD, NMU), Ilana Engelbrecht (MSc, NMU), Tayla Ginsburg (MSc, NMU), Laurie Johnson (MSc, UCT), Danielle van den Heever (MSc, NMU) Oyena Masiko (CB MSc, UCT).