Identifizierung und Charakterisierung von Nahrungsgebieten von Seevögln in Auftriebsgebieten: Bedeutung von biologischen und hydrographischen Parametern für den Nahrungserwerb auf See

This thesis investigates the foraging behaviour of three seabird species, the African penguin (Spheniscus demersus) and the Cape gannet (Morus capensis) in the Benguela upwelling system as well as the Peruvian booby (Sula variegata) in the Humboldt Current. Biological and hydrographic parameters were considered when evaluating the characteristics of foraging areas and the behaviour of the species studied. Foraging areas used by the birds as well as the birds' diving behaviour were assessed by using data logger technologies and results obtained through these methods were combined with diet sampling and observations from ship-based surveys. Seabirds in both upwelling regions are confronted with changes in environmental conditions and the birds' reaction to alterations in hydrography as well as food limitations have been evaluated. African penguins in Namibia were studied at three breeding colonies which differ in numbers of breeding pairs as well as in oceanographic parameters due to distinct bathymetry. At Mercury Island, studies were performed in two consecutive years allowing for inter-annual comparisons, especially taking into account differences in food availability due to sulphide eruptions in 2005. African penguins at Mercury Island showed similar foraging behaviour as conspecifics in South Africa (Wilson 1985 ; Wilson et al. 1988; Ryan et al. 2004; Petersen et al. 2006), foraging within a range of maximum 32 km from the colony (median of 22 and 21 km in 2005 and 2006) and diving to maximum depths of about 75 m. Considering only dives deeper than 10 m depth (defined as foraging dives), most dives reached depths of 25 – 35 m. In both years, birds frequented the same area north-west of the island in order to forage. In 2005, sulphide eruptions caused hypoxic conditions in the entire water column, dissolved oxygen concentrations being as low as 2 ml/l in surface waters and below 0.2 ml/l at the sea bottom. Birds were almost exclusively feeding on pelagic goby (Sufflogobius bibarbatus), a demersal fish species able to tolerate low-oxygen conditions (Currie et al. submitted). In 2006, birds were feeding on anchovy (Engraulis capensis) and sardine (Sardinops sagax) in addition to pelagic goby. The higher percentage of pelagic prey was also reflected in the diving behaviour, birds diving to lower depths during foraging dives (median 35 vs. 27 m in 2005 and 2006, respectively). Studies at Halifax and Possession Islands included only small numbers of birds, but differences in foraging behaviour as well as in diet composition were observed and may be related to varying bathymetry around the islands. Food limitation seems to affect African penguins at all breeding colonies along the Namibian coast, not only during sulphide eruptions, and has to be considered as a key factor for the population decline observed in Namibia. In order to monitor environmental conditions, the use of seabirds as indicators has been proposed (Wilson 1992; Montevecchi 1993; Wilson et al. 1994; Weimerskirch et al 1995; Wilson et al. 2002; Fedak 2004). In this study, the use of data loggers enabled fine-scale temperature measurements during the diving in penguins. These in situ measurements of water temperature were included in an oceanographic model, showing small scale variations in spatial as well as temporal extensions. Cold upwelling cells were identified along the coast and the impact of local wind patterns on processes of temperature distribution became apparent. Relatively small numbers of logger-equipped birds would be needed for synoptical oceanographic monitoring around penguin colonies and would lead to a better understanding of oceanographic processes influencing seabird foraging. The ability to cover larger distances within single foraging trips and its implication for foraging in areas of reduced food abundance was studied in Cape gannets in the Benguela system. Lower prey availability during the breeding season 2005 due to sulphide eruptions led to diving activity over larger areas and birds were feeding on smaller prey individuals. Birds' foraging took place mainly along the coast but several birds covered large areas offshore. They foraged over water masses with different temperature regimes and presumably encountered a different prey composition over the shelf break. Birds reached distances of almost 200 km away from the colony and about 80 km off the coast. Site fidelity presented by several birds feeding at similar sites in consecutive trips indicates predictable prey but, as in the case of African penguins, numbers of gannet breeding pairs show declining trends in Namibia which is presumably also due to food limitation. Peruvian boobies breeding in northern central Chile were observed foraging almost exclusively in coastal waters. Food availability seemed to be favourable within large bays due to localised upwelling at protruding points and birds left for short foraging trips, which indicates high food abundance. A high variability in prey organisms obtained by the birds was observed between several years studied. Numbers of breeding pairs at Isla Pájaros varied strongly between years and breeding ceased completely during an El Niño year in 2002. Nonetheless, seabirds in the Humboldt upwelling system show fast population recoveries after strong El Niño events which indicates their adaption to this frequently occurring phenomenon. The importance of predictable food abundance in upwelling systems for seabird foraging is pointed out in this study. All species studied showed similar foraging behaviours, commuting between colonies and predictable feeding sites, foraging mostly over coastal upwelled waters. Additionally, site fidelity underlined the predictability of prey patches within the upwelling systems. Birds were able to switch to different prey items and to adapt foraging and diving behaviour to varying environmental conditions. Nonetheless, it may be doubted whether birds will successfully cope with alterations in the ecosystems that could lead to further reduced prey abundance in the future.Die vorliegende Arbeit untersucht die Ernährungsweisen dreier unterschiedlicher Seevogelarten: des Afrikanischen Pinguins (Spheniscus demersus) und des Kaptölpels (Morus capensis) im Auftriebsgebiet des Benguelastroms vor der südwestlichen Küste Afrikas und des Guanotölpels (Sula variegata) im Auftriebsgebiet des Humboldtstroms vor der Westküste Südamerikas. Die Arbeit berücksichtigt sowohl biologische als auch hydrographische Parameter für die Beurteilung der Nahrungsgebiete auf See und des Verhaltens der genannten Arten. Zur Datenerhebung diente die Loggertechnologie; die erlangten Ergebnisse wurden durch Nahrungsproben sowie Beobachtungen auf See komplementiert. Seevögel in beiden Auftriebsgebieten sind von Veränderungen in ihrer Meeresumwelt betroffen. Die daraus resultierende Nahrungsverknappung und das dadurch bedingte Verhalten der Tiere wurden untersucht. Die Untersuchungen am Afrikanischen Pinguin wurden in drei Brutkolonien entlang der namibischen Küste durchgeführt. Unterschiede sind sowohl in der Anzahl der Brutvögel in den Kolonien zu finden als auch in den ozeanographischen Bedingungen in der Umgebung der Brutinseln. Das Verhalten der Pinguine auf Mercury Island wird vor allem im Hinblick auf unterschiedliche Nahrungsverfügbarkeit, verursacht durch Schwefelausbrüche im Jahre 2005, in zwei aufeinanderfolgenden Jahren verglichen. Das Ernährungsverhalten der Afrikanischen Pinguine in Namibia ist vergleichbar mit dem ihrer Artgenossen in Südafrika (Wilson 1985; Wilson et al. 1988; Ryan et al. 2004; Petersen et al. 2006). Das Nahrungsgebiet der Pinguine auf Mercury Island erstreckte sich über eine maximale Distanz zur Kolonie von 32 km (mediane Distanzen 22 und 21 km in 2005 und 2006) und die maximal erreichte Tauchtiefe betrug 75 m. Während Nahrungstauchgängen, definiert als Tauchgänge mit einer Mindesttiefe von 10 m, erreichten die Tiere vorzugsweise Tiefen von 25 bis 35 m. In beiden Jahren frequentierten die Tiere ein Gebiet nordwestlich der Brutinsel Mercury Island. Im Jahr 2005 verursachten Schwefelausbrüche hypoxische bis anoxische Verhältnisse in der Wassersäule; Konzentrationen von gelöstem Sauerstoff betrugen weniger als 2 ml/l an der Oberfläche und weniger als 0.2 ml/l in größeren Tiefen. Die Pinguine erbeuteten fast ausschließlich Meeresgrundeln (Sufflogobius bibarbatus), eine bodennah lebende Fischart, die geringe Sauerstoffmengen im Wasser toleriert (Currie et al. submitted). Im Jahr 2006 bestand die Nahrung der Pinguine hingegen neben Meeresgrundeln aus Sardellen (Engraulis capensis) und Sardinen (Sardinops sagax). Der höhere Anteil pelagischer Beutearten spiegelte sich auch im Tauchverhalten der Tiere wider. Pinguine tauchten in geringere Tiefen (Median 35 vs. 27 m in 2005 und 2006) während der Nahrungssuche. Die nur wenige Tiere umfassenden Studien auf Halifax und Possession Island ließen Unterschiede im Ernährungsverhalten und in der Nahrungszusammensetzung zwischen den Kolonien erkennen. Dies kann auf Unterschiede in der Bathymetrie in der Umgebung der verschiedenen Inseln zurückgeführt werden. Afrikanische Pinguine scheinen in allen Brutkolonien entlang der namibischen Küste von Nahrungsverknappung betroffen zu sein. Dies ist nicht nur während Schwefelausbrüchen der Fall, wie im Jahre 2005 beobachtet, sondern stellt ein Kernproblem dar, welches der wichtigste Faktor für die dramatische Abnahme des Pinguinbestandes in Namibia ist. Die Überwachung von ökologischen Parametern durch Untersuchungen an Seevögeln wurde bereits mehrfach diskutiert (Wilson 1992; Montevecchi 1993; Wilson et al. 1994; Weimerskirch et al. 1995; Wilson et al. 2002; Fedak 2004). Die in dieser Studie verwendeten Datenlogger erlauben eine feinskalige Analyse der Wassertemperaturen in den Nahrungsgebieten der Afrikanischen Pinguine. Die während der Tauchgänge gemessenen Temperaturen wurden mit Hilfe eines ozeanographischen Modells interpoliert, welches feinskalige Veränderungen räumlicher sowie zeitlicher Form im Untersuchungsgebiet aufzeigt. Kältere, vom Auftrieb herrührende Wasserlinsen befanden sich entlang der Küste, wohingegen Wassermassen fernab der Küste höhere Temperaturen aufwiesen. In größeren Tiefen erfolgte eine zunehmende Durchmischung. Bereits relativ wenige mit Datenloggern ausgerüstete Pinguine liefern ausreichend Daten, um die ozeanographischen Bedingungen in der Umgebung der Brutkolonien zu beurteilen. Die daraus resultierenden Kenntnisse der Auftriebsprozesse tragen zu einem besseren Verständnis der Nahrungsökologie der Tiere bei. Kaptölpel im Auftriebsgebiet des Benguelastroms sind in der Lage, durch Flüge über große Distanzen ihre Nahrungssuche zu optimieren und gegebenenfalls Nahrungsknappheit zu umgehen. Während der Schwefelausbrüche im Jahr 2005 nutzten die Tiere größere Gebiete zur Nahrungssuche und die Nahrungsbestandteile bestanden aus kleineren Beuteindividuen. Die Tiere erbeuteten ihre Nahrung in unterschiedlichen Wassermassen entlang der Küste und an der Schelfkante. Die maximalen Entfernungen von der Kolonie betrugen 200~km und die Tiere erreichten bis zu 80~km von der Küste entfernte Meeresgebiete. Das Aufsuchen gleicher Gebiete bei aufeinander folgenden Nahrungsflügen deutet auf eine vorhersehbare Beuteverfügbarkeit hin. Dennoch ist, wie auch im Fall des Afrikanischen Pinguins, eine drastische Bestandsabnahme des Kaptölpels in Namibia zu beobachten, die vermutlich ebenfalls von Nahrungsverknappung herrührt. Guanotölpel im Humboldtstrom suchten fast ausschließlich entlang der Küste ihre Nahrung. Die Nahrungsverfügbarkeit scheint positiv von Küstenlinie und von Buchten beeinflusst zu sein, die einen verstärkten Auftrieb und eine Ansammlung von Nahrungsorganismen verursachen. Die Tölpel unternahmen zahlreiche, relativ kurze Nahrungsflüge und erbeuteten unterschiedliche Fischarten in den verschiedenen Jahren. Auch die Anzahl der auf der Isla Pájaros brütenden Guanotölpel variiert jährlich. Im Jahr 2002, einem Jahr mit einem ausgeprägtem El-Niño-Phänomen, wurde die bereits begonnene Brut aufgegeben. Trotz solcher Ereignisse scheinen die Vögel im Humboldtstrom an Veränderungen angepasst, u.a. verdeutlicht durch den schnellen Anstieg der Brutpaarzahlen. Das Vorkommen von vorhersehbaren Nahrungsquellen in Auftriebsgebieten scheint von großer Bedeutung für die hier untersuchten Arten zu sein. Das Ernährungsverhalten der unterschiedlichen Arten ähnelt sich in beiden Auftriebsgebieten. Die Tiere begeben sich relativ direkt von ihren Brutkolonien zu den Nahrungsgebieten auf See und suchen ihre Nahrung hauptsächlich an Auftriebszellen entlang der Küste oder der Schelfkante. Die Vorhersehbarkeit von Nahrungsansammlungen in diesen Gebieten wird auch durch das wiederholte Aufsuchen der gleichen Gebiete unterstrichen. Die untersuchten Seevogelarten können zwischen verschiedenen Nahrungsorganismen wechseln und ihr Such- und Tauchverhalten unterschiedlichen Gegebenheiten anpassen. Trotzdem kann bezweifelt werden, dass die hier untersuchten Seevogelarten in der Lage sind, fortschreitende Veränderungen in ihrer Umgebung und die daraus vermutlich resultierende Nahrungsknappheit zu verkrafte

A royal penguin eudyptes schlegeli in the Falkland Islands?

The Royal Penguin Eudyptes schlegeli breeds only on Australia’s Macquarie Island and its nearby islets, about 1 200 km southwest of New Zealand. Vagrant Royal Penguins have been reported elsewhere in Australia, New Zealand and Antarctica. Reports of Royal Penguins from other subantarctic islands, including Heard, Prince Edward and Marion Islands, South Georgia and the Falkland Islands are controversial, as these penguins could also be aberrant Macaroni Penguins E. chrysolophus, and species determination can be difficult because of high variation in facial colour in both species. We discuss here the recent sighting of an apparent immature Royal Penguin on New Island, Falkland Islands. A simultaneously visiting adult male Macaroni Penguin allowed a size comparison between the two individuals. This could be the first documented sighting of a vagrant Royal Penguin in the Neotropical region.info:eu-repo/semantics/acceptedVersio

Is penguin circovirus circulating only in the antarctic circle? Lack of viral detection in namibia

The known host range of circoviruses is continuously expanding because of more intensive diagnostic activities and advanced sequencing tools. Recently, a new circovirus (penguin circovirus (PenCV)) was identified in the guano and cloacal samples collected from Adélie penguins (Pygoscelis adeliae) and chinstrap penguins (Pygoscelis antarcticus) in Antarctica. Although the virus was detected in several asymptomatic subjects, a potential association with feather disease was speculated. To investigate the occurrence and implications of PenCV in other penguin species located outside of Antarctica, a broad survey was undertaken in African penguins (Spheniscus demersus) on two islands off the southern Namibian coast. For this purpose, specific molecular biology assays were developed and validated. None of the 151 blood samples tested positive for PenCV. Several reasons could explain the lack of PenCV positive samples. African penguins and Pygoscelis species are separated by approximately 6000 km, so there is almost no opportunity for transmission. Similarly, host susceptibility to PenCV might be penguin genus-specific. Overall, the present study found no evidence of PenCV in African penguin colonies in Namibia. Further dedicated studies are required to assess the relevance of PenCV among different penguin species

Initial evaluation of the care and rehabilitation success of Cape Cormorants Phalacrocorax capensis rescued from Robben and Jutten islands, South Africa, in January 2021

The population of the endangered Cape Cormorant Phalacrocorax capensis more than halved over the last three decades (BirdLife International 2018a). In January 2021, nearly 2 000 Cape Cormorant chicks were found abandoned, suffering from dehydration and heat stress, at two important nesting sites. The chicks were rescued and rehabilitated by the Southern African Foundation for the Conservation of Coastal Birds (SANCCOB, Cape Town, South Africa). About half (53.7%) of the cormorant chicks were successfully rehabilitated and released back into the breeding colonies. This study found a direct link between the initial body mass of cormorant chicks admitted to the rehabilitation centre and their probability of surviving during rehabilitation, with birds that were initially heavier having a greater probability of eventual release. Most cormorant chicks that died (80.7%) did so within the first 5 days of admission. This rescue required SANCCOB to care for and rehabilitate the largest number of Cape Cormorant chicks that has ever been admitted to its rehabilitation centre at one time, making it the first rescue of its kind. Despite the presumably limited positive impact on overall population numbers of Cape Cormorants, the rescue campaign improved SANCCOB’s preparedness to respond successfully to future disaster events and to deal with different species, both locally and globally

Good days, bad days: wind as a driver of foraging success in a flightless seabird, the southern Rockhopper Penguin

Due to their restricted foraging range, flightless seabirds are ideal models to study the short-term variability in foraging success in response to environmentally driven food availability. Wind can be a driver of upwelling and food abundance in marine ecosystems such as the Southern Ocean, where wind regime changes due to global warming may have important ecological consequences. Southern rockhopper penguins ( Eudyptes chrysocome ) have undergone a dramatic population decline in the past decades, potentially due to changing environmental conditions. We used a weighbridge system to record daily foraging mass gain (the difference in mean mass of adults leaving the colony in the morning and returning to the colony in the evening) of adult penguins during the chick rearing in two breeding seasons. We related the day-to-day variability in foraging mass gain to ocean wind conditions (wind direction and wind speed) and tested for a relationship between wind speed and sea surface temperature anomaly (SSTA). Foraging mass gain was highly variable among days, but did not differ between breeding seasons, chick rearing stages (guard and crèche) and sexes. It was strongly correlated between males and females, indicating synchronous changes among days. There was a significant interaction of wind direction and wind speed on daily foraging mass gain. Foraging mass gain was highest under moderate to strong winds from westerly directions and under weak winds from easterly directions, while decreasing under stronger easterly winds and storm conditions. Ocean wind speed showed a negative correlation with daily SSTA, suggesting that winds particularly from westerly directions might enhance upwelling and consequently the prey availability in the penguins' foraging areas. Our data emphasize the importance of small-scale, wind-induced patterns in prey availability on foraging success, a widely neglected aspect in seabird foraging studies, which might become more important with increasing changes in climatic variability

Vaccination of African penguins (Spheniscus demersus) against high-pathogenicity avian influenza

DATA AVAILABILITY STATEMENT : The data that support the findings of this study are available from the corresponding author upon reasonable request.BACKGROUND : High-pathogenicity avian influenza (HPAI) has become a conservation threat to wild birds. Therefore, suitable vaccine technology and practical application methods require investigation. METHODS : Twenty-four African penguins (Spheniscus demersus) were vaccinated with either a conventional inactivated clade 2.3.4.4b H5N8 HPAI whole virus or a tobacco leaf-produced H5 haemagglutinin-based virus-like particle (VLP). Six birds received a second dose of the inactivated vaccine. Antibody responses were assessed and compared by employing haemagglutination inhibition tests. RESULTS : A second dose of inactivated vaccine was required to induce antibody titres above the level required to suppress virus shedding, while a single dose of VLP vaccine produced these levels by day 14, and one bird still had antibodies on day 430. LIMITATIONS : Bacterial contamination of the VLP vaccine limited the monitoring period and sample size in that treatment group, and it was not possible to perform a challenge study with field virus. CONCLUSION : VLP vaccines offer a more practical option than inactivated whole viruses, especially in logistically challenging situations involving wild birds.NRF-DSI SARChI and Health and Welfare Sector Education and Training Authority.https://wileyonlinelibrary.com/journal/vetrhj2023Centre for Veterinary Wildlife StudiesProduction Animal StudiesSDG-03:Good heatlh and well-bein

Geographic variation in the trophic ecology of an avian rocky shore predator, the African black oystercatcher, along the southern African coastline

International audienceThe reflection of baseline isotopic signals along marine food chains up to higher trophic levels has been widely used in the study of oceanic top predators but rarely for intertidal predators. We investigated variation in the δ13C and δ15N ratios of a sedentary, rocky shore predator, the African black oystercatcher Haematopus moquini, over ~2000 km of the southern African coastline, which is characterized by strong biogeographic patterns in primary productivity and intertidal communities. Blood and feathers from breeding adults and chicks and muscle tissues from primary prey items (mussels and limpets) were sampled between southern Namibia and the southeast coast of South Africa. 15N enrichment was observed between the southeast and west coasts in oystercatcher tissues and their prey, mirroring an isotope shift between the oligotrophic Agulhas Current on the east coast and the eutrophic Benguela upwelling system on the west coast. Oystercatcher blood showed δ13C values that varied between those of the carbon-depleted mussels and the carbon-enriched limpets along the coastline, which reflected changes in the proportion of grazers and filter feeders in the oystercatcher diet across the sampling range. The geographic shift in diet, dominated by mussels on the west coast and composed of mixed proportions of mussels and limpets on the southeast coasts, strongly reflected regionally high abundances of the invasive Mediterranean mussel Mytilus galloprovincialis. Finally, isotope signatures of blood and feathers displayed a strong correlation throughout the study area, indicating seasonal stability in environmental conditions and feeding habits of the adults. There were, however, local discrepancies on the south coast that indicated movement of adults occurred outside the breeding season possibly in response to a lower abundance of food in this region. Overall, the results indicate that the influence of regional oceanic conditions on the base of the food web can penetrate to the predator level, but that local effects can be incorporated within this pattern

Is Penguin Circovirus Circulating Only in the Antarctic Circle? Lack of Viral Detection in Namibia

The known host range of circoviruses is continuously expanding because of more intensive diagnostic activities and advanced sequencing tools. Recently, a new circovirus (penguin circovirus (PenCV)) was identified in the guano and cloacal samples collected from Adélie penguins (Pygoscelis adeliae) and chinstrap penguins (Pygoscelis antarcticus) in Antarctica. Although the virus was detected in several asymptomatic subjects, a potential association with feather disease was speculated. To investigate the occurrence and implications of PenCV in other penguin species located outside of Antarctica, a broad survey was undertaken in African penguins (Spheniscus demersus) on two islands off the southern Namibian coast. For this purpose, specific molecular biology assays were developed and validated. None of the 151 blood samples tested positive for PenCV. Several reasons could explain the lack of PenCV positive samples. African penguins and Pygoscelis species are separated by approximately 6000 km, so there is almost no opportunity for transmission. Similarly, host susceptibility to PenCV might be penguin genus-specific. Overall, the present study found no evidence of PenCV in African penguin colonies in Namibia. Further dedicated studies are required to assess the relevance of PenCV among different penguin species

Is penguin circovirus circulating only in the Antarctic circle? Lack of viral detection in Namibia

The known host range of circoviruses is continuously expanding because of more intensive diagnostic activities and advanced sequencing tools. Recently, a new circovirus (penguin circovirus (PenCV)) was identified in the guano and cloacal samples collected from Adélie penguins (Pygoscelis adeliae) and chinstrap penguins (Pygoscelis antarcticus) in Antarctica. Although the virus was detected in several asymptomatic subjects, a potential association with feather disease was speculated. To investigate the occurrence and implications of PenCV in other penguin species located outside of Antarctica, a broad survey was undertaken in African penguins (Spheniscus demersus) on two islands off the southern Namibian coast. For this purpose, specific molecular biology assays were developed and validated. None of the 151 blood samples tested positive for PenCV. Several reasons could explain the lack of PenCV positive samples. African penguins and Pygoscelis species are separated by approximately 6000 km, so there is almost no opportunity for transmission. Similarly, host susceptibility to PenCV might be penguin genus-specific. Overall, the present study found no evidence of PenCV in African penguin colonies in Namibia. Further dedicated studies are required to assess the relevance of PenCV among different penguin species.The number of circovirus species is continuously expanding thanks to improved diagnostic and sequencing technologies. Recently, a new circovirus (penguin circovirus (PenCV)) was identified in the guano and cloacal samples collected from Adélie penguins (Pygoscelis adeliae) and chinstrap penguins (Pygoscelis antarcticus) in Antarctica, and a potential association with disease was proposed. The present study investigates the occurrence of PenCV infection in Namibian African penguin (Spheniscus demersus) colonies. No evidence of viral circulation was observed, suggesting that PenCV distribution could be limited to Antarctica or to particular penguin species.MeerWissen-African–German Partners for Ocean Knowledge Initiative,National Geographic Society and IAEA Peaceful Uses Initiative (PUI) VETLAB Network.https://www.mdpi.com/journal/animalsCentre for Veterinary Wildlife StudiesProduction Animal Studie