Conserving Benguela endemic seabirds
All three seabirds endemic to the Benguela upwelling ecosystem that rely on anchovies and sardines are threatened by a reduction in the availability of their preferred prey. Small pelagic fish have greatly reduced in abundance off the southern African west coast, where fishing effort is concentrated and most seabird breeding islands are located. Fish stocks have increased off the south coast, where fishing pressure is low but there are very few suitable bird breeding locations. The main challenge is to ensure adequate spatial management of this fishery. To this end, it is important to understand how the at-sea distribution of seabirds overlaps with fish distribution and fishing effort.
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 African Penguin Sphensicus demersus, Cape Cormorant Phalacrocorax capensis and Cape Gannet Morus capensis. And it is not only these species that depend on small pelagic fish that are in trouble. Populations of Bank Cormorants Phalacrocorax neglectus, which feed on a diverse array of demersal prey, also have decreased along the South African west coast, but increased locally along the south coast. 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, Taryn Morris) and DEA (Azwianewi Makhado and Rob Crawford), as well as several post-doctoral students.
Activities in 2017
- After completing his PhD at the Fitz, Alistair McInnes took up a post-doctoral position at NMU to study 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 is using cameras and GPS loggers to see how hard penguins have to work to catch prey.
- Another NMU postdoc, Dr Giannina Passuni, worked with Lorien Pichegru and NMU’s Nadine Strydom to investigate the stomach contents of anchovies eaten by African Penguins to understand the diet of the penguins’ main prey. She is also investigating water quality and plankton abundance around St Croix Island. She will link her results to oceanographic data from SAEON to understand how environmental conditions affect pelagic fish and their prey.
- The experimental closure of commercial fishing for small pelagic fish around key penguin breeding islands continued in 2017. In Algoa Bay, penguins breeding on St Croix Island again decreased their foraging effort during closures. Richard Sherley’s paper in Proceedings of the Royal Society suggested that high environmental variability between years and colonies made it hard to demonstrate benefits of closures on penguin chick condition, and advocated controlling for environmental conditions to pin-point the effect of the closures. Despite this, the Department of Agriculture, Forestry and Fisheries decided to re-open St Croix Island to fishing for 2018-2020.
- PhD student Gwendoline Traisnel published on African Penguin personalities in Ethology. Individual penguins vary in how they respond to a human intruder, with shy birds tending to be better parents than more aggressive birds, especially when food is scarce. Aggressive individuals may spend more energy defending their nests, limiting their investment in foraging effort.
- Gwendoline also published a note in Marine Ornithology about plumage aberrations in African Penguins. Few individuals are resighted across years, suggesting potentially high adult mortality.
- Lorien Pichegru’s new PhD student Katharina Reusch (NMU) started a project investigating the foraging ecology of Kelp Gulls Larus dominicanus. With visiting scientist Dr Nicolas Suarez from the Centro Patagonico in Argentina, she deployed GPS recorders and collected stomach 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.
- Pierre Pistorius continued to study Cape Gannets, collecting tracking and demographic data at the Bird Island colony in Algoa Bay. Post-doctoral student, Andrea Thiebault, deployed tiny microphones and video-recorders on some tracked birds to study at-sea acoustic communication.
- Danielle Van Den Heever completed data collection on the at-sea habitat use by Wedge-tailed Shearwaters Ardenna pacifica breeding at Reunion and the Seychelles.
- Illana Engelbrecht started a 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 continued their long-term study of Cape Gannets breeding on Malgas Island. In recent years, most adult gannets provisioning chicks spend more energy than they gain through foraging, with long-term fitness cost. In 2017, they deployed GPS on individuals of known-age to explore how experience influences foraging success.
- Lorien Pichegru highlighted the very high levels of predation on the Cape Gannets breeding on Malgas Island. Kelp Gulls and Cape Fur Seals Arctocephalus pusillus have unsustainable impacts on the population and need active management.
- Davide Gaglio was awarded his PhD, and published papers on the diet of Greater Crested Terns (PLoS One), their ability to catch multiple prey (Ostrich) and the impact of kleptoparasitism when breeding with and without Hartlaub’s Gulls Chroicocephalus hartlaubi (Behavioural Ecology).
- Alistair McInnes’s paper in the Proceedings of the Royal Society, London demonstrated that penguins foraging in groups on bait balls had increased catch rates compared to birds foraging individually. This paper attracted widespread media coverage, including in New Scientist.
- A paper from Alistair’s PhD published in Marine Ecology Progress Series showed that penguins from Bird Island, Algoa Bay, exploit an upwelling cell of high localised productivity, helping to offset the impacts of fishing activity on this colony.
- Lorien Pichegru’s findings on the impacts of seismic surveys on African Penguins published in Scientific Reports may have wide implications, as seismic surveys are increasing globally in frequency and intensity, with limited understanding of their impact on seabirds.
- Richard Sherley’s paper on the threats facing Bank Cormorants was published in the leading conservation journal, Conservation Biology.
- Several students presented papers or posters at the 16th South African Marine Sciences Symposium in Port Elizabeth in July and at the 6th Bio-logging Conference in Hamburg in September.
- Pierre Pistorius coordinated a well-attended workshop at the South African Marine Science Symposium on seabird and seal research within the Benguela region. The main aim was to develop an inventory of all tracking data within the region which will be used in future studies to identify Ecologically and Biologically Significant Areas (EBSAs) for conservation-based marine spatial planning.
- 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.
- MSc student Jonathan Botha graduated with distinction for his thesis comparing the foraging behaviour of Cape Gannets during the guard and post-guard phases. He reported some spatial and temporal segregation between the sexes in Marine Ecology Progress Series.
BirdLife International; BirdLife South Africa; DST-NRF CoE grant; Raggycharters Whale Watching.
Prof. Peter Ryan (FIAO, UCT)
Prof. Res Altwegg (SEEC, UCT)
Dr Maëlle Connan (NMU)
Dr Timotheé Cook (FIAO, UCT)
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 Giannina Passuni (NMU)
Dr Lorien Pichegru (NMU)
Dr Pierre Pistorius (NMU)
Dr Richard Sherley (U. Bristol)
Dr Ross Wanless (FIAO, UCT and BLSA)
Students: Davide Gaglio (PhD, UCT), Katharina Reusch (PhD, NMU), Rabi’a Rijklief (PhD, NMU), Gwendoline Traisnel (PhD, NMU), Jonathan Botha (MSc, NMU), Ilana Engelbrecht (MSc, NMU), Tayla Ginsburg (MSc, NMU), Noelle Tubbs (MSc, UCT), Danielle van den Heever (MSc, NMU) Oyena Masiko(CB MSc, UCT).