Behaviour of the jackass penguin chick
TL;DR: The ontogeny of Jackass Penguin Spheniscus demersus chick behaviour follows the order of development determined for Adelie Pygoscelis adeliae and Yelloweyed Megadyptes antipodes Penguins.
Abstract: Summary Seddon, P. J. & Y. van Heezik. 1993. Behaviour of the Jackass Penguin Chick. Ostrich 64:8-12. The ontogeny of Jackass Penguin Spheniscus demersus chick behaviour follows the order of development determined for Adelie Pygoscelis adeliae and Yelloweyed Megadyptes antipodes Penguins. Feeding and comfort behaviours occur from day one, followed by locomotion and aggressive behaviours. Jackass Penguin chicks are largely inactive during both the day and at night; chicks less than 20 days old are usually prone beneath the attending adult. Begging, feeding and preening are the major chick activities. Begging and feeding become restricted to late afternoon and evening following the commencement of the post-guard phase when chicks are between 26–45 days old. Feeding episodes last on average less than 30 minutes. The frequency of preening increases as chicks moult from about 40 days.
TL;DR: From 1989 to 2004, the breeding success of African penguins Spheniscus demersus at Robben Island, South Africa was significantly related to estimates of the abundance of both their main prey species, anchovy and sardine, and to the combined biomass of these species.
Abstract: From 1989 to 2004, the breeding success of African penguins Spheniscus demersus at Robben Island, South Africa was significantly related to estimates of the abundance of both their main prey species, anchovy Engraulis encrasicolus and sardine Sardinops sagax , and to the combined biomass of these species. When the combined spawner biomass of fish prey was less than 2 million ton, pairs fledged an average of 0.46 chicks annually. When it was above 2 million ton, annual breeding success had a mean value of 0.73 chicks per pair. Given previously estimated values of survival and age at first breeding, these levels of breeding success are inadequate to sustain the African penguin population. With the higher level of breeding success, an equilibrium situation might be attained if adult survival could be increased by 6–7% per annum. Attempts to reduce mortality of penguins have included the collection, cleaning and return to the wild of oiled birds, culling of Cape fur seals Arctocephalus pusillus pusillus seen preying on penguins around breeding localities and control of the spread of disease. Management of the purse-seine fishery should ensure adequate escapement of fish to maintain the combined biomass of anchovy and sardine above 2 million ton. The maintenance of suitable breeding habitat and removal of feral predators from breeding localities will also be important in improving breeding success.
TL;DR: Breeding success and chick-fledging rates increased during the study period and showed positive relationships with local food availability, indexed through the annual industrial catch of anchovy made within 56 km (30 nautical miles) of the colony.
Abstract: Population trends of African penguins Spheniscus demersus in the Western Cape, South Africa, and their breeding success have been linked to the abundance of their main prey, sardine Sardinops sagax and anchovy Engraulis encrasicolus. During the late 1990s and early 2000s, both fish species increased markedly in abundance, but after 2004, sardine biomass decreased to below average levels. In addition, adults of both stocks were principally located to the east of Cape Agulhas from 2001 to 2009 and were thus distant from seabird colonies on South Africa's West Coast. The number of African penguin pairs counted at Robben Island from 2001 to 2009 and the fledging period of chicks from successful nests increased and decreased in apparent response to the biomass of sardine prior to each breeding season, possibly linked through adult condition at the onset of breeding. Breeding success and chick-fledging rates increased during the study period and showed positive relationships with local food availability, indexed through the annual industrial catch of anchovy made within 56 km (30 nautical miles) of the colony. In addi- tion, chick-fledging rates were depressed in 2-chick broods during years when anchovy con- tributed <75% by mass to the diet of breeding birds. Previously reported relationships between the overall abundance of forage fish in South Africa and penguin breeding success were not sup- ported. Taken together, these results highlight the combined importance of ensuring adequate local food availability for seabirds during the reproductive cycle and safeguarding regional prey abundance during the non-breeding season.
TL;DR: If a similar large spill should occur in the future, every effort should be made to treat the oiled birds as quickly as possible to reduce the risk of their suffering a similar reduction in breeding productivity.
Abstract: About 19 000 African Penguins (Spheniscus demersus) were oiled when the bulk ore carrier MV Treasure sank off the west coast of South Africa in June 2000. Of these, more than 17 000 Penguins were cleaned, rehabilitated and released back to the wild. The breeding success of these birds was compared with unoiled birds and birds oiled during other oil-spills, by measuring fecundity, hatching success and fledging success from 2001 to 2005 on Robben Island. Fledging success averaged 61% in birds that were not oiled in the Treasure spill and 43% in birds oiled during the Treasure event, with a large proportion of the reduction attributable to higher mortality of older chicks. Factors that may have contributed to differential fledging success include long mean intervals between capture and cleaning (22 days) and between capture and release (48 days) for birds oiled in the Treasure spill. One implication of these results is, if a similar large spill should occur in the future, every effort should be made to treat the oiled birds as quickly as possible to reduce the risk of their suffering a similar reduction in breeding productivity. Further, the other interventions, such as relocation of unoiled birds and captive-rearing of orphaned chicks may need to receive higher priority than hitherto.
TL;DR: An investigation into the effectiveness of providing artificial nests for the endangered African Penguin at a colony on Robben Island, South Africa, supports findings from Namibia, and also supports the continued use of artificial nests as a conservation tool throughout the range of the species.
Abstract: Loss of nesting habitat threatens many cavity nesting birds worldwide and has contributed to the decline of several species of burrow-nesting seabirds. Replacing lost habitat with artificial nesting structures is considered to be a useful conservation intervention. Here we report on an investigation into the effectiveness of such a strategy – providing artificial nests for the endangered African Penguin (Spheniscus demersus) at a colony on Robben Island, South Africa. The re-colonisation of Robben Island by breeding African Penguins in the 1980s was partly attributed to the availability of shaded nesting habitat under introduced vegetation. However, the suitability of this habitat had not been tested empirically. In addition, artificial nests have been present at Robben Island since 2001, but whether they were a viable means of providing improved nesting habitat was not known. The reproductive output of African Penguins was monitored on Robben Island from 2001 to 2010. Breeding success varied between years but, overall, was within the range of figures previously reported for the species. Relative to pairs in nests under vegetation, birds occupying artificial nests and nests in abandoned buildings had increased nesting survival during chick-rearing, with 9 and 13% more chicks fledged per egg hatched over the study period. These artificial structures seem to offer the advantages of shelter from the weather and protection from predators, without the risks of collapse associated with natural burrows in non-guano substrates. This study supports findings from Namibia, and also supports the continued use of artificial nests as a conservation tool throughout the range of the species.
TL;DR: Combining the data on survival with that on breeding success indicates that 1,000 hand-reared chicks will produce around 1,220 chicks themselves over their lifetimes, making this a worthwhile conservation intervention.
Abstract: Some 2,000 orphaned chicks of African Penguins Spheniscus demersus were hand-reared and released back into the wild on Robben and Dassen Islands following the Treasure oil spill in June 2000. Of these chicks, 1,787 were flipper banded. This paper reports on the subsequent survival rate and breeding success of those individuals seen on Robben Island from 2001–2006. Survival to breeding age and their subsequent breeding success of hand-reared chicks was no different from that of naturally-reared chicks. Over a four-year period, pairs where at least one partner was a hand-reared chick produced an average of more than 1.6 chicks per year. Combining the data on survival with that on breeding success indicates that 1,000 hand-reared chicks will produce around 1,220 chicks themselves over their lifetimes, making this a worthwhile conservation intervention.
TL;DR: Seven major types of sampling for observational studies of social behavior have been found in the literature and the major strengths and weaknesses of each method are pointed out.
Abstract: Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
TL;DR: It is possible that the slower growth rates in the field may be due to the necessity for parents to guard chicks from predators, after the onset of the chicks' full thermoregulatory abilities.
Abstract: Energetic requirements for growth of the jackass penguin (Sphenisaa demersus) were studied by hand-rearing captive chicks, and by observing growth rates, feeding rates and meal sizes in the field. Daily gain in mass was highest in the period of linear growth (23-55 days). Daily relative growth decreased with age. Food intake and guano production increased from 20-40 days and thereafter remained constant. Relative food intake decreased with age. Digestive efficiency increased with age, and energetic content of guano decreased with age. Chicks in the field grew at a slower rate than the hand-reared birds and were estimated to have consumed approximately half as much food by time of fledging. Feeding of chicks in the field occurred mainly in the afternoon and daily food intake increased with age. It is possible that the slower growth rates in the field may be due to the necessity for parents to guard chicks from predators, after the onset of the chicks' full thermoregulatory abilities.
TL;DR: The Jackass penguin appears to be relatively thermolabile, which would facilitate both energy conservation in water and resistance to heat stress on land.
Abstract: Penguins tend to be overinsulated for life on land. A study of the Jackass penguin Spheniscus demersus was undertaken to investigate the behavioural adaptations that enable the species to cope with the exigencies of a hot, terrestrial environment. The Jackass penguin is mainly crepuscular and nocturnal at its breeding stations. The numbers of birds present on land are highest at night and lowest during the day. The majority of birds leaving a breeding colony do so just after dawn. Birds begin to return to the colony during the late afternoon. The frequency of displays is highest at dawn and from dusk to midnight. This activity cycle enables birds not engaged in incubation or chick guarding to avoid conditions promoting heat stress. Birds remaining in the colony during the day employ strategies such as burrow-nesting, body-orientation and evaporative cooling to reduce the effects of high insolation. Compared to the ambient, the microclimate of burrows is more constant; relative humidity is higher; air temperatures fluctuate less; and wind effect is negligible. Most important, birds nesting in burrows are protected from direct insolation. Egg and nest-air temperature in a burrow are relatively constant. Burrows facing east are cooler than those facing west. However this does not influence burrow-orientation, which is determined by the slope of the ground. Birds exposed to high insolation orientate with their backs to the sun. The lightly feathered areas of the body are shaded. This facilitates heat loss by convection and re-radiation from these shaded surfaces. In this position dorsal surface temperature regularly exceeds body temperature. It is suggested that heat gain from the dorsal surface is restricted by efficient insulation, primarily an adaptation to the aquatic environment. On overcast days orientation is non-directional. In the early morning when ambient temperatures are relatively low, the birds also orientate with their backs to the sun. This is interpreted as sunbathing. Body temperatures were significantly higher on a hot than on a cool day. The Jackass penguin appears to be relatively thermolabile. This would facilitate both energy conservation in water and resistance to heat stress on land. The overall thermoregulatory strategies of the Jackass penguin for life in two different environments are discussed.
TL;DR: Comparisons of survival in control and experimental nests with varying degrees of sibling asymmetry indicate that it is the extent of hatching asynchrony that affects the ability of the smaller sibling to compete for food and that will produce sibling differences in the risk of starvation.
Abstract: We used survival analysis to examine the fates of Jackass Penguin (Spheniscus demersus) chicks on Dassen Island, off the west coast of South Africa. There were two distinct phases of chick loss. The first, when chicks were 0-34 days old, involved losses primarily due to burrow collapse, exposure and drowning, and accidental death in the nest. This mortality was influenced strongly by nest-site characteristics. Overall reproductive success was lowest in open nests, intermediate in burrows, and highest in rock nests. The probability of chick death due to flooding was highest for burrows in shell/guano conglomerate, whereas the risk of burrow collapse was highest in sand. Burrows in high-density colonies had a greater likelihood of collapsing after heavy rain than burrows in low-density areas. The second phase occurred 42-90 days after hatch, when losses were almost entirely due to starvation. Comparisons of survival in control and experimental nests with varying degrees of sibling asymmetry indicate that it is the extent of hatching asynchrony that affects the ability of the smaller sibling to compete for food and that will produce sibling differences in the risk of starvation. Chicks in two-chick control nests starved at higher frequencies than chicks in less asynchronous experimental broods. Received 24 April 1990, accepted 17 December 1990. STUDIES of the breeding success of colonial seabirds may be hampered by the complexity with which many factors influence reproduc- tive success (Davis and McCaffrey 1986). In par- ticular, the inability to identify specific causes of chick mortality limits our knowledge of the factors that influence breeding failure. Recent studies of the Jackass Penguin (Sphe- niscus demersus) provided estimates of breeding success (Frost et al. 1976a, Cooper 1980, Randall and Randall 1981, Randall 1983, LaCock et al. 1987) without identifying specific causes of mortality or the timing of losses. No published study of the Jackass Penguin has considered either the timing of separate causes of chick mortality or the effect of sibling asymmetries on the probability of survival. We used survival analysis techniques (Davis and McCaffrey 1986) to (1) quantify the causes and timing of prefledging Jackass Penguin chick mortality; (2) investigate the effect of hatching order, chick number, and sibling size asym- metries on chick loss in natural asynchronous nests; (3) compare chick survival in natural asynchronous nests and experimental nests having different degrees of asynchrony; and (4) examine the influence of nest site on chick mor-
TL;DR: The hypothesis that most birds breed at a time when reproductive potential is most fully realised is examined by using the numbers of Jackass Penguins returning to the island per 24 hour period as an index of the number of birds breeding.
Abstract: Jackass Penguins breed throughout the year but show seasonal preferences. I examined the hypothesis that most birds breed at a time when reproductive potential is most fully realised. By using the numbers of Jackass Penguins returning to the island per 24 hour period as an index of the number of birds breeding, I found that most penguins on the island bred when chick growth was maximal and chick mortality was minimal. The diet of Jackass Penguins was determined by stomach pumping 556 birds. More than 95% of their diet, by weight, consisted of pelagic schooling fish. The local abundance of these fish seemed to determine the breeding success of the Jackass Penguin.