Restoration of oiled African penguins Spheniscus demersus a decade after the Apollo Sea spill

The bulk ore carrier Apollo Sea sank south-west of Dassen Island off western South Africa in June 1994, oiling approximately 10 000 African penguins Spheniscus demersus, most of which were collected from Dassen Island. A total of 4 076 de-oiled penguins was released with flipper bands. From 1994 to 2005, follow-up research using re-sighting and capture-mark-recapture methods indicated that about 73% of the de-oiled penguins observed back at Dassen Island attempted to breed, and were thus successfully restored into the breeding population. For de-oiled breeders, the median interval between their first recorded sighting and first recorded breeding attempt was 11 months, indicating a short-term delay in restoration. At least 45% of the de-oiled breeders were still being re-sighted five years after their release, and a minimum of 4% survived into their ninth year. These results represent the most successful restoration estimates anywhere in the world. The proportion of de-oiled juvenile penguins re-sighted back at Dassen Island and recorded breeding was lower than that of birds in adult plumage. De-oiled non-breeders spent significantly more time along the shore and less time within breeding colonies than de-oiled breeders. The mean proportion of de-oiled breeders that abstained from breeding each year during the study period was greater than expected. There was a negative relationship between breeding and subsequent survival and breeding, suggesting a cost of reproduction for de-oiled birds.     

Initial impact of the Treasure oil spill on seabirds off western South Africa

On 23 June 2000, the bulk ore carrier MV Treasure sank off western South Africa between Dassen and Robben islands, which individually currently support the largest and 3^rd largest colonies of African penguins Spheniscus demersus. Subsequently, more than 19 000 penguins were oiled, almost twice the previous highest number of seabirds oiled during a single event in southern Africa (10 000 penguins after the sinking of the Apollo Sea in June 1994). About 19 000 oiled penguins were collected for cleaning and care and about 150 oiled adults died in the wild. Some 19 500 unoiled penguins were caught at Dassen and Robben islands and relocated to Port Elizabeth, 800 km to the east, to remove them from waters affected by the oil. Of all penguins caught, which amounted to 20% of the total species population, less than 2 000 died within the first month, considerably less than in the Apollo Sea spill. This can be attributed to improved transport of penguins and the rapid arrival at rescue centres of experts able to administer emergency care. However, resources were severely extended and mortality would probably have been considerably higher had large numbers of birds not been removed from the area affected by the oil. Many relocated birds returned to their home islands within a month of being released, but considerable disruption of pair bonds is expected to result from mortality, different periods in captivity and disruption of moult cycles. This is likely to result in decreased breeding success. Recruitment to colonies will also be reduced by substantial loss of chicks and eggs. Although more than 3 000 orphaned chicks were collected for captive rearing, an estimated 4 000 died at the islands before they could be rescued. Up to 20% of bank cormorants Phalacrocorax neglectus at Robben Island, the 3^rd largest colony of the species in South Africa, died. There was low success in catching oiled cormorants and in saving those that were caught. Of 53 grown birds of four species of cormorant that were oiled and caught, only 17 survived. Captive rearing of bank cormorant chicks, which it was feared may have been orphaned, proved more successful. Spilt oil had minor impact on gulls, terns and shorebirds in the region.     

Impact of flipper-banding on breeding success of African penguins Spheniscus demersus at Robben Island: comparisons among silicone rubber bands,stainless-steel bands and no bands

From 2001 to 2006, two new designs of flipper bands made from silicone rubbers were tested on African penguins Spheniscus demersus at 365 nests on Robben Island, South Africa. We compared, over six years, the breeding success, from hatching to fledging, of three different groups of penguins: those with rubber bands (117 nests), with conventional stainless-steel bands (103 nests) and without bands (145 nests). There were no significant differences in breeding success between the three groups, suggesting that neither the currently used steel bands, nor either of the new rubber-band designs, were harmful during the seasons investigated. The rubber bands caused less wear of feathers and less drag on a model penguin than the steel bands. In captivity, the behaviours of African penguins fitted with rubber bands were not noticeably different to those of unbanded birds.     

Recent trends in numbers of four species of penguins at the Prince Edward Islands

Four species of penguin breed regularly at South Africa's Prince Edward Islands: king penguin Aptenodytes patagonicus, gentoo penguin Pygoscelis papua, macaroni penguin Eudyptes chrysolophus and southern rockhopper penguin E. chrysocome. In December 2008, it was estimated that some 65 000 pairs of king penguins were incubating eggs at Marion Island, the larger of the two islands in the group, and 2 000 pairs at Prince Edward Island. At Marion Island from 1987 to 2008, there was no long-term trend in numbers of king penguin chicks that survived to the end of the winter period, but there was considerable fluctuation in chick production in the 1990s. It was roughly estimated that on average 88% of king penguin chicks survived the winter period (from April to September/October). Numbers of gentoo penguins at Marion Island decreased from more than 1 300 pairs in the mid-1990s to fewer than 800 pairs in 2003, and then increased to almost 1 100 pairs in 2008 as breeding success improved. Between 1994/1995 and 2008/2009, numbers of macaroni and southern rockhopper penguins at Marion Island decreased by about 30% and 70% respectively. In 2008/2009, some 290 000 pairs of macaroni penguins bred at this island, mostly in two large colonies where there was a progressive decrease in the density of nests. At both these colonies, decreases in numbers breeding followed outbreaks of disease. Inadequate breeding success has influenced the decreases of macaroni and rockhopper penguins. In 2008/2009, some 42 000 pairs of southern rockhopper penguins bred at Marion Island and 12 000 pairs of macaroni penguins and 38 000 pairs of southern rockhopper penguins at Prince Edward Island.     

Season of moult of African penguins at Robben Island,South Africa,and its variation, 1988–1998

Counts of African penguins Spheniscus demersus in immature and adult plumage in the feather-shedding phase of moult were made at Robben Island at two-weekly intervals over a 10-year period between 1988 and 1998. For both age-classes, most birds moulted between November and January, although small numbers moulted throughout the year. In most years, the peak moult was in late November or December. Immature birds had a secondary peak in March. In 1994/95 for adults, and 1995/96 for immature birds, moult was less synchronized than in other years. This probably resulted from oiling of about 2 400 penguins in June 1994, following the sinking of the Apollo Sea. Half of those birds were cleaned and released. Their subsequent moult may have been earlier than normal.     

Factors influencing growth of the African penguin colony at Boulders,South Africa, 1985–1999

This paper reports on growth of the Boulders colony of African penguins Spheniscus demersus from inception in 1985 to the present. More than 900 pairs now breed there. Growth of the colony slowed in 1995 and 1996 and reversed in 1998, coinciding with periods of low abundance of Cape anchovy Engraulis capensis off South Africa. In December 1996, penguins were excluded from a portion of land where they had formerly bred. They responded by increasing the density of their nests in other areas and expanding their area of breeding longshore. These patterns indicate that food and not space are currently controlling colony growth rate. Much of the colony growth probably results from immigration of first-time breeders from other colonies. Of immigrants, 70–80% may be from Dyer Island to the south-east, where numbers of penguins have decreased. Boulders also is frequently visited by penguins from other colonies, and by rehabilitated birds.     

Studies on the Adelie penguin at cape Royds 1964–65 and 1965–66

The adult population of the colony, egg sizes, incubation watches, and egg and chick mortality are considered for the 1964–65 and 1965–66 breeding seasons. In 1964–65 1,051 breeding pairs were recorded and 1,467 chicks survived to leave the colony: this represents 67.5% of eggs laid. In 1965–66 1,186 breeding pairs successfully reared 1,390 chicks: 57.0% of eggs laid. Egg and chick mortality over four breeding seasons is considered, with special reference to ice conditions in McMurdo Sound. Dimensions of 349 eggs are given, including those for clutches produced by 33 known females in successive seasons. Breeding success of known pairs of birds is discussed. Birds breeding for the first time appear to lay a single, small egg and to be unsuccessful; experienced breeders which change their mate are usually unsuccessful. Observations are made on chick plumage and panting. A prone sleeping posture in which the bill is directed towards the axilla is described and illustrated. Some observations on the South Polar Skua are recorded.     

Populations of Surface-nesting Seabirds at Marion Island, 1994/95–2002/03

During the 1990s and early 2000s, populations of surface-nesting seabirds at Marion Island showed different trends, but for the majority of species numbers decreased. Reduced numbers of gentoo penguins Pygoscelis papua, eastern rockhopper penguins Eudyptes chrysocome filholi, Crozet shags Phalacrocorax [atriceps] melanogenis and probably macaroni penguins E. chrysolophus are most plausibly attributed to an altered availability of food. Decreases in numbers of dark-mantled sooty albatrosses Phoebetria fusca, light-mantled sooty albatrosses P. palpebrata, southern giant petrels Macronectes giganteus and possibly northern giant petrels M. halli may have resulted from mortality of birds in longline fisheries. However, populations of wandering Diomedea exulans and grey-headed Thalassarche chrysostoma albatrosses fluctuated around a stable level. Numbers of Subantarctic skuas Catharacta antarctica and kelp gulls Larus dominicanus breeding at Marion Island also decreased. Kerguelen Sterna virgata and Antarctic S. vittata terns remain scarce at the island. Trends for king penguins Aptenodytes patagonicus were not reliably gauged, but numbers probably remained stable or increased. There were large fluctuations in numbers of king penguin chicks surviving to the end of winter.     

Diving behaviour of African penguins: do they differ from other Spheniscus penguins?

African penguins Spheniscus demersus closely resemble Magellanic S. magellanicus and Humboldt S. humboldti penguins and have similar breeding and feeding ecologies. Adults feed on pelagic schooling fish in continental shelf waters, but African penguins have been reported to have shallower dive angles and remain submerged longer for dives to a given depth than their congeners. The few data for African penguins were gathered using relatively large time-depth recorders. We measured diving behaviour of 36 African penguins provisioning small chicks at three colonies near Cape Town, South Africa. Maximum and mean dive depths were 69m and 14m respectively. Diving took place mainly during the day. Although dive depths differed between colonies, there were no significant differences in dive duration or maximum, median or mean depth. Total dive duration, descent time, bottom time, ascent time and dive angle all were strongly correlated with the maximum depth attained. The diving behaviour of African penguins is similar to that of its congeners. Diving performance probably was compromised by the data-logger used in the previous study. Comparative data from Humboldt penguins also indicate potential biases in an earlier study of this species. Care is needed when comparing the diving performance of penguins measured using different loggers.     

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 Namibia's 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.     

Congruent,decreasing trends of gentoo penguins and Crozet shags at sub-Antarctic Marion Island suggest food limitation through common environmental forcing

Numbers of gentoo penguins Pygoscelis papua and Crozet shags Phalacrocorax [atriceps] melanogenis breeding annually at Marion Island, one of South Africa's Prince Edward Islands in the South-West Indian Ocean, were strongly correlated over 19 split-years from 1994/1995 to 2012/2013. Both species decreased between the mid-1990s and the mid-2000s, exhibited a partial recovery in the late-2000s and then decreased to their lowest recorded levels in 2012/2013. In both instances, the partial recoveries in the late-2000s were associated with improved breeding success. At a colony of gentoo penguins, breeding success was negatively correlated with the date of arrival of adults to breed. Gentoo penguins and Crozet shags are demersal feeders in inshore waters around Marion Island and there is considerable overlap in the composition of their diets. Therefore, trends in their populations may be driven by food availability, which is likely to be influenced by benthic production around the island. We propose that, in South Africa, and based on the current assessment, the Crozet shag, which elsewhere breeds only at the Crozet Islands, is now Critically Endangered, and the more widely ranging gentoo penguin is Endangered.     

Potential impacts of invasive Spartina alterniflora on spring bird communities at Chongming Dongtan,a Chinese wetland of international importance

Invasive smooth cordgrass (Spartina alterniflora, hereafter Spartina) has been expanding rapidly in the estuarine wetlands at Chongming Dongtan (East China) at the expense of native sea-bulrush (Scirpus mariqueter, hereafter Scirpus) and common reed (Phragmites australis, hereafter Phragmites). To examine the potential impacts of the Spartina invasion on bird diversity, we compared the abundance and species richness of birds in habitats created by Spartina, Phragmites, Spartina mixed with Phragmites, Scirpus, and the bare intertidal zone at Chongming Dongtan in spring 2008. Most birds were recorded in the native habitats, with songbirds and breeding birds being most abundant in the Phragmites habitats, and waterbirds and migrants being most abundant in the Scirpus habitats and bare intertidal zone. Both species number and population densities of birds were lower in the exotic Spartina habitats than in the other four habitats. Although some songbirds and breeding birds used the Spartina-invaded habitats, and even preferred Spartina-invaded habitats to Scirpus habitats and bare intertidal zone, their densities were lower in the Spartina-invaded habitats than in the native Phragmites habitats. This might have resulted from the dense Spartina stands restricting bird movement and providing insufficient useable food for most birds. We conclude that the spread of exotic Spartina has negative impacts on local bird communities. Because Chongming Dongtan is an important stopover site for energy replenishment of shorebirds in the East Asian–Australasian Flyway, urgent measures are needed to control further spread of Spartina and to restore the native habitats for birds.     

Age at breeding of crowned cormorants Phalacrocorax coronatus

Between 1991 and 1995,242 crowned cormorant Phalacrocorax coronatus chicks were banded at Malgas Island with metal and colour rings. At least 10 subsequently bred before 4 April 1996. First-year birds had juvenile plumage, but when about one year old they attained the plumage of immature birds and of non-breeding adults. The youngest age at breeding was about one year, but many birds did not breed until aged 1½–2 years and some may not have bred before they were three years old.     

Recent population trends of sooty and light-mantled albatrosses breeding on Marion Island

Sub-Antarctic Marion Island is one of the few islands where both species of Phoebetria albatrosses breed sympatrically. The last published assessment of their population trends, which reported counts up to 2008, concluded that the numbers of breeding pairs of sooty albatross P. fusca (Endangered) were decreasing, whereas numbers of light-mantled albatross P. palpebrata (Near Threatened) were increasing. Extending the counts to 2014 reversed these trends, with numbers of sooty albatrosses increasing from 2006 to 2014, and numbers of light-mantled albatrosses decreasing from 2007 to 2014. Confidence in island-wide counts is low due to the cryptic nature of the albatrosses on their largely inaccessible cliff-side nest sites, as well as counts for sooty albatrosses taking place late in the incubation period when 10?20% of nests have already failed. Given the greater conservation concern for the sooty albatross, we recommend that dedicated annual counts be conducted during the early incubation period, and be repeated shortly after the chicks hatch (late December), mid-way through the nestling period (late February) and prior to fledging (late April), to give a better idea of breeding success. Count zones also should be revised to facilitate more accurate counts, ensuring more reliable estimates of sooty albatross population trends at Marion Island.     

Foraging ecology of an endemic shorebird, the African Black Oystercatcher (Haematopus moquini) on the south–east coast of South Africa

We investigated small–medium (1–300 km) scale variation in the foraging ecology of the African Black Oystercatcher during its breeding season, using traditional diet analysis coupled with carbon and nitrogen stable isotope analysis. Fieldwork was conducted between January and March 2006 and 2007, on rocky shores on the south–east coast of South Africa at East London, Kenton and Port Elizabeth. Middens of shelled prey left by adults feeding their chicks were collected from five territories and the abundances of the collected prey on the foraging areas were estimated using quadrats. Blood samples from 45 birds (16 females, 10 males and 19 chicks) and tissues from the predominant prey species on the territory of each breeding pair were collected for isotope analysis. The Manly–Chesson selectivity index revealed that adults feed their chicks preferentially with the limpet Scutellastra cochlear and the Mediterranean mussel Mytilus galloprovincialis, if available. A slight enrichment in the ¹⁵N stable-carbon isotope signature was observed towards the west in both prey and oystercatchers. Differences in isotope signatures between males and females from the same breeding pair indicate sex-related differences in the diet. Both had signatures indicating a mixed diet, but with males exhibiting a signature closer to that of limpets and females closer to that of mussels. In the single case where mussels were rare on the feeding territory, the two members of a pair showed carbon signatures which were identical and very similar to that of limpets. These results indicate dietary partitioning between genders in breeding pairs.     

Birds and conservation significance of the Namib Desert's least known coastal wetlands: Baia and Ilha dos Tigres,Angola

The Ilha dos Tigres of Angola is the only sandy island off the coast of the 2 000km-long Namib Desert and it remains the least known coastal wetland on a desert coast rich in shorebirds. Two surveys of the Baia dos Tigres region in 1999 and 2001 indicated a rich wetland bird diversity consisting of 25 species, with a total of 11 000 birds, at a density of 33 birds km^?1 of beach. We established breeding by three species of seabirds — two cormorants and the great white pelican Pelecanus onocrotalus — and confirmed northward range extensions for two of these species. The region supports seven regionally threatened Red Data birds. Several threatened marine turtles occur at the nearby Cunene River mouth, and given the possibility that turtles and other Red Data birds may breed at Ilha dos Tigres, it is recommended that it should become an integral part of the Iona National Park on the adjacent mainland.     

A helping hand: artificial nest site provisioning increases breeding success of a tropical seabird

Common white terns Gygis alba lay a single egg balanced on rocks or branches and consequently are at risk of low nesting success. A novel technique of hollowing out coconut husks and providing artificial nest sites was developed on Cousine Island, Seychelles. Our study aimed to critically assess whether common white tern nesting success differed between artificial and natural nest sites. For natural nest sites, nesting success and the stage of nest failure were also compared between seasons, nest heights, and tree species. Finally, we compared results from our study to those of a study conducted 10 years ago on the same island. Nesting success differed significantly between artificial nests and natural nests, with the success of artificial nests nearly double that of natural nests. Hatching success was similar for artificial and natural nests (65% and 52% respectively), suggesting coconut husks do not reduce egg losses, but rather provide secure perches for young chicks. Most natural nest failures occurred during the egg phase (70%), followed by the youngest chick phase (21%). Of the eggs that hatched in natural nests, 61% fledged successfully. Tree species and season significantly influenced nesting success for natural nests and nest height varied significantly between tree species. Higher nesting success was observed during the mixed seasonal period (50%) followed by the cooler, windier and drier South-East Monsoon season (33%). The hotter and more humid North-West Monsoon period had the lowest nesting success (20%). Comparisons of nesting success at natural and artificial nest sites with the earlier study did not differ significantly, despite a smaller population of common white terns being present on the island at that stage. Our results support the use of artificial nest sites to improve nesting success for this species and serve as a model for similar species currently under threat.     

Nest Densities of the Wandering Albatross Diomedea Exulans at the Prince Edward Islands,Estimated Using Gps

Hand-held Global Positioning System (GPS) receivers provide opportunities for detailed and rapid mapping of features, including biological ones, further enhanced by the removal during 2000 of "selective availability". GPS was used to map, describe and compare nest densities within wandering albatross Diomedea exulans colonies at subantarctic Marion and Prince Edward islands. On Prince Edward Island, the coordinates of 1 061 wandering albatross nests were determined and, on Marion Island, 1 779 nests. For describing nest densities of wandering albatrosses, a 50-m grid is recommended, at which scale, the densest area of Prince Edward Island was in Albatross Valley, where the area of the colony was 46 ha and nest density was 22.3 nests ha^?1. For Marion Island, the total area of the wandering albatross colonies was 306 ha and the nest density was 5.8 nests ha^?1. In the three study colonies there (Macaroni Bay, 28 nests; Sealer's Beach, 117 nests; Goney Plain, 140 nests), the density statistics did not differ greatly from the overall densities on the island, with overall mean densities of 4.9, 5.7 and 8.0 birds ha^?1 respectively. Although comparisons with nest densities at other breeding colonies are uncertain because of differing methods of computing them, the nest densities in Albatross Valley lie within the reported ranges for other colonies of great albatrosses.     

Estimates of numbers of kelp gulls and Kerguelen and Antarctic terns breeding at the Prince Edward Islands, 1996/1997–2008/2009

Breeding numbers of Laridae and other surface-nesting seabirds have been monitored at sub-Antarctic Marion Island since 1996/1997 and counts of breeding birds were made at nearby Prince Edward Island in December 2001 and December 2008. Four species are regular breeders at the islands: Subantarctic skua Catharacta antarctica, kelp gull Larus dominicanus, Antarctic tern Sterna vittata and Kerguelen tern S. virgata. The latter three species currently each have populations of below 150 breeding pairs at the islands. Kelp gull numbers appear to be relatively stable though they may have decreased since the 1980s. Kerguelen tern numbers decreased and then recovered at Marion Island, but numbers of the species have declined at Prince Edward Island and it maintains a tenuous foothold there. The small Antarctic tern population appears to be stable.     

African penguins as predators and prey – coping (or not) with change

African penguins Spheniscus demersus live in the Benguela and western Agulhas ecosystems off southern Africa. Their numbers decreased throughout the 20^th century from at least 1.5 million to about 0.18 million adults, although different regional trends were apparent. They feed to a large extent on shoaling epipelagic fish, notably anchovy Engraulis capensis and sardine Sardinops sagax, and regional trends in the abundance of penguins are associated with trends in the abundance and distribution of these prey fish. Many first-time breeders emigrate from colonies where feeding or other conditions at the time are unfavourable to more favourable breeding localities. This has led to both the extinction and formation of colonies. Food now may limit colonies at relatively small sizes, a fact attributable to industrial fisheries reducing the densities of forage fish. African penguins share their habitat with several other predators, with which they compete for food and breeding space. One of these, the Cape fur seal Arctocephalus p. pusillus, increased through the 20^th century to 1.5 – 2 million animals at its close. Reported observations of predation by fur seals on seabirds have increased in recent decades and threaten the continued existence of small colonies of penguins. Stochastic modelling suggests that colonies of 10 000 pairs have a 9% probability of extinction in 100 years, so smaller populations should be regarded as "Vulnerable". However, in a period of prolonged food scarcity off southern Namibia, the regional population decreased from more than 40 000 pairs in 1956 to about 1 000 pairs in 2000, and many colonies numbering less than 1 000 pairs became extinct. The minimum viable population for African penguins is currently considered to be >40 000 pairs, likely of the order of 50 000 pairs, a figure equivalent to its level in 2000. The chance of survival of the species through the 21^st century is tenuous.