Jessica Kemper

Fragmentation of South African renosterveld shrublands: effects on plant community structure and conservation implications

Abstract Nearly 85% of South Coast renosterveld, a fire-prone shrubland, has been replaced by agriculture; the remaining areas are small fragments scattered throughout agricultural lands. Because nearly all of the remaining vegetation is required to fulfil a modest reservation target, conservation of these fragments will be central to any implementation plan. To assess the condition and, therefore, the conservation potential of these fragments, we investigated the community patterns, species diversity and representation of biological attributes in 23 renosterveld fragments. Communities in large fragments were more similar to each other than those in small fragments. There were no significant linear relationships between species diversity and fragment area. We found weak fragmentation effects in attribute representation. Numbers of alien graminoid species and total alien species, and frequency of individuals of geophyte species increased with decreasing fragment size. Frequency of individuals and percentage cover of species with seeds that are dispersed for short distances, increased with decreasing fragment size, while percentage cover of perennial graminoids decreased. Small fragments are highly disturbed by grazing, trampling, crop spraying and frequent fires, but retain a similar community structure to large fragments that presumably represent the pre-agricultural matrix vegetation. Therefore, all remnants of renosterveld, irrespective of fragment size, should be considered conservation-worthy.

A description of the functional vegetation pattern of a semi-arid floodplain, South Africa

The floodplain ecosystem of the Nyl River is located in a semi-arid region of South Africa where water limits both human development and ecosystem functioning. Proposed upstream impoundments threaten the ecosystems functioning and hence its conservation value and eco-tourist potential. Articulation of these threats to the floodplain ecosystem requires a predictive understanding of the relationships between the biota and hydro-geomorphic processes. This study provides the basis for the establishment of these relationships by presenting a description of the plant assemblages of the Nyl River floodplain, identifying environmental correlates of this vegetation pattern, and by distinguishing functional plant groups. A correspondence analysis identified three major vegetation associations on the floodplain ecosystem: near-channel sites, hydromorphic sites and sodic sites. Geomorphic landform type, soil moisture and soil texture were the best correlates of the vegetation pattern. Elevation above the channel and distance from the channel were poor correlates of vegetation pattern. The distribution of functional groups, which were defined by plant life forms, showed that the near-channel sites were dominated by prostrate and decumbent grasses, hydromorphic sites by erect grasses, and sodic sites by a variety of succulent life forms. The plant-environment relationships recognized suggest that future distributions of functional plant groups may provide a sensitive index of the impacts of anticipated reductions in run-off.

Surviving off junk: low-energy prey dominates the diet of African penguins Spheniscus demersus at Mercury Island, Namibia, between 1996 and 2009

The diet of African penguins Spheniscus demersus in Namibia consisted mainly of sardine Sardinops sagax in the 1950s. Since the collapse of pelagic fish stocks in the 1970s, birds fed mainly on bearded (pelagic) goby Sufflogobius bibarbatus, a low-energy prey species. We present diet data for African penguins breeding at Mercury Island, the largest colony for this species in Namibia, between 1996 and 2009. Bearded goby was the main prey item throughout the study period, both in terms of frequency of occurrence (67.8%; SD 31.2) and in terms of mass (59.2%; SD 31.5). Diet composition varied throughout the year as well as between years; birds occasionally fed on a variety of fish species other than bearded goby. In Namibia, poor prey abundance is considered as a major factor contributing to the decline of penguin numbers after the collapse of the sardine stocks. However, bearded goby appears to be relatively abundant along Namibias southern coast and low prey quality rather than low abundance appears to be a key factor influencing population dynamics of African penguins and other marine top predators in southern Namibia.

Trends in numbers of Cape Cormorants (Phalacrocorax capensis) over a 50-year period, 1956–57 to 2006–07

Abstract The population trend of Cape Cormorants (Phalacrocorax capensis), a species endemic to southern Africa and that feeds mainly on shoaling pelagic fish, is described for a 50-year period, from 1956–57 to 2006–07. The main breeding localities for the species are grouped in three regions in the Benguela upwelling ecosystem: guano platforms off central Namibia, islands off southern Namibia and islands off South Africas Western Cape Province. From 1956–57 to 1978–79, the numbers breeding off Namibia increased, as a result of increased availability of breeding space and adequate supplies of food. In the same period, numbers remained stable in the Western Cape. Numbers decreased off southern Namibia in the early 1980s and off central Namibia in the early 1990s, when environmental perturbations reduced the availability of food. Numbers decreased in the Western Cape in the early 1990s, following periods of scarcity of anchovy (Engraulis encrasicolus), an important prey item, and an outbreak of avian cholera caused by the bacterium Pasteurella multocida. They remained low as cholera outbreaks continued and some pelagic fish were displaced to the east beyond the foraging range of breeding Cormorants. The overall population of Cape Cormorants was of the order of 100000 pairs in 1956–57, increased to ∼250000 pairs in the 1970s, but reverted to ∼100000 pairs in 2005–06.

Age at first breeding of the African Penguin

Numbers of breeding pairs of African Black Oystercatchers showed a highly significant increase at Cape Agulhas over a 24year study period. Mean numbers of fledglings per pair did not increase correspondingly but showed a cyclic tendency, peaking twice, with a slight overall decline. The increase in the frequency of repeat clutches was close to significant. Nest failures were ascribed largely to human disturbance. Indications of increasing public awareness about the sensitivity of breeding oystercatchers were noted as well as increasing adaptability to human presence among some birds, whereas other birds moved their nests further away from this disturbance. In view of the closure of the Overberg coast to recreational vehicles from 20 February 2002 and the relative importance of the area for the conservation of oystercatchers, this long-term study represents an important baseline against which to measure change.

Storms and heat limit the nest success of Bank Cormorants: implications of future climate change for a surface-nesting seabird in southern Africa

AbstractThe Bank Cormorant Phalacrocorax neglectus is endemic to the Benguela Upwelling System of southern Africa. Most breeding colonies occur on offshore rocks, islands or man-made structures close to the high-water mark. Despite adaptations for breeding close to the water, nests can be lost to storms. Using data from two colonies where food is not considered limiting, we present a comparative study on nest survival in Bank Cormorants. Using a combination of the Mayfield method and parametric survival analysis, nest success was compared in nests on man-made structures at Robben Island, South Africa, where birds breed during the austral winter, with nests on man-made and natural structures at Mercury Island, Namibia, where Bank Cormorants breed during the austral summer. Overall, the probability of a nest surviving the breeding attempt was lower at Robben Island than at Mercury Island in all three seasons. Nest failures at Robben Island were related to wave heights and air temperature, with trends to suggest reduced chick survival in years where major storm events occurred during peak breeding. A heat wave appeared to cause major chick mortality at Mercury Island in 2005. Nest survival was relatively invariable between years at the main site monitored on Mercury Island, where nests were partially sheltered from the sun, but breeding productivity was poor in comparison to other cormorant species. Winter breeding in South Africa may increase the risk from storms but reduce the risk of heat exposure. An understanding of the impact of stochastic events on Bank Cormorants may be important in safe-guarding the continued survival of the species, particularly in light of the risks posed by future climate change.ZusammenfassungStürme und Hitze limitieren den Bruterfolg der KüstenscharbePhalacrocorax neglectus: Auswirkungen des Klimawandels auf einen nahe des Meeresspiegels brütenden Seevogel im südlichen Afrika Die Küstenscharbe Phalacrocorax neglectus ist endemisch für das Auftriebsgebiet des Benguela-Stroms im südlichen Afrika. Die meisten Brutkolonien befinden sich auf Felsen, Inseln und künstlichen Strukturen kurz über der Hochwassermarke. Trotz Anpassungen an das Brüten nahe der Wasserlinie werden Nester oft durch Stürme zerstört. In dieser Studie vergleichen wir den Bruterfolg der Küstenscharbe in zwei unterschiedlichen Kolonien, in denen keine Nahrungsknappheit vorliegt. Mit Hilfe der Mayfield-Methode und parametrischer Tests zur Berechnung der Überlebensrate wurden der Bruterfolg von Tieren auf Robben Island, Südafrika, und Mercury Island, Namibia verglichen. Auf Robben Island brüten die Tiere im dortigen Winter auf künstlichen Strukturen, während die Vögel auf Mercury Island während der Sommermonate sowohl auf natürlichen als auch auf künstlichen Strukturen brüten. In allen drei Untersuchungsjahren lag der Bruterfolg auf Robben Island unter dem von Mercury Island. Nestverluste auf Robben Island wiesen einen Zusammenhang mit Wellenhöhe und Lufttemperaturen auf und höhere Kükenverlusten wurden in Jahren beobachtet, in denen große Sturmereignisse mit der Hauptbrutperiode zusammenfielen. Eine Hitzewelle in 2005 verursachte ein großes Kükensterben auf Mercury Island. Der Bruterfolg schwankte nur gering auf Mercury Island in der Hauptbrutkolonie, wo Nester teilweise geschützt und im Schatten lagen. Im Vergleich zu anderen Kormoranarten war der Bruterfolg aber eher gering. Das Brüten im Winter bei Tieren in Südafrika verringert die Gefahr der Verluste durch Hitzwellen, erhöht aber die Gefahr von Nestverlusten durch Stürme. Ein besseres Verständnis der Einflüsse von stochastischen Wetterereignissen auf den Bruterfolg dieser bedrohten Art ist besonders wichtig in Hinblick auf den Klimawandel und damit einhergehenden Veränderungen im Wetter.

Effect of Age and Breeding Status on Molt Phenology of Adult African Penguins (Spheniscus Demersus) in Namibia

Abstract We analyzed the seasonality of molt of African Penguins (Spheniscus demersus) in adult plumage and used information derived from banded individuals to examine the relationship between age, breeding status, and timing of molt in Namibia. Molt seasonality was bimodal, with a major molt peak in the austral autumn and a minor peak in midsummer. African Penguins younger than four years—and, therefore, unlikely to be sexually mature—molted in early January, at the same time as juvenile African Penguins. Birds aged between four and six years molted either in summer or autumn and were likely to be individuals making the transition from nonbreeder to breeder. African Penguins older than six years, considered to be breeders, molted, on average, in early May. Most birds that had been recorded breeding within 12 months of molt molted between March and May. Summer breeding in Namibia appears to force breeders to delay molt until autumn. There was individual variation in molt seasonality that we could not explain by age alone. Estimates of the proportion of potential breeders in the population derived from molt phenology and from the molt histories of banded, known-age individuals were likely to be underestimates and suggested that some adults of breeding age defer breeding.

A new mainland breeding locality for African Penguins, Bank and Crowned Cormorants on the Namib desert coast

PA Bartlett1, J-P Roux1*, R Jones1 and J Kemper2, 3 1 Ministry of Fisheries and Marine Resources, Luderitz Marine Research, PO Box 394, Luderitz, Namibia 2 African Penguin Conservation Project, c/o Ministry of Fisheries and Marine Resources, PO Box 394, Luderitz, Namibia 3Avian Demography Unit, University of Cape Town, Rondebosch 7701, South Africa * Corresponding author, e-mail: jproux@mfmr.gov.na