Research Results
Research on chick growth and condition, combined with data from nine years of nest monitoring, has helped formulate models of the relationships between climate, prey availability and penguin survival. The scientists have found potential correlations between breeding success and prey biomass during the breeding season, as well as in the months between moulting and the start of breeding. Higher prey availability before the breeding season, appears to have an effect on breeding success for that year. This finding was unexpected, but may allow projections of breeding success from the condition of adult birds and prey biomass before the breeding season commences. Overall, there has been a steady decline in average breeding success on Robben Island and it appears this decline is linked to the availability of prey in the area, specifically anchovy and sardine.
In the years up to 2005, the breeding success of birds oiled in the Treasure spill versus those that were not was significantly reduced. This trend was not observed in 2007-2008, but as of 2010 there is again a clear difference in the breeding success of previously oiled birds versus non-oiled. It is hypothesized that this difference in breeding success is most apparent when food availability is decreased and birds have to use the maximum forage effort to find enough food for their chicks.
Earthwatch scientists have successfully developed and tested new prototype silicone rubber flipper bands for African penguins (Spheniscus demersus) and they have become used on a nationwide scale since 2008. To date, volunteers have made nearly 20,000 re-sightings of banded penguins (around 8,000 different birds). In 2009, 871 re-captures were recorded, corresponding to 463 individual penguins.
Earthwatch volunteer-collected data has aided development of an automatic recognition system which records patterns of spots on the chests of adult birds through digital photography. This technique is still being tested and refined, but eventually it may be possible to monitor remotely more than 90% of the penguins on the island.
The project compares breeding success of penguins based on use of natural or man-made nest sites. Data indicates that breeding success is better for birds that nest in disused buildings and in man made nest boxes placed by project volunteers. The project will continue to investigate whether or not one type of artificial nest is better than another.
Earthwatch volunteers also performed counts of all visible wading birds around the coast of the island helping to provide a baseline for the number of birds present throughout the year. Some of these observed birds include African Black Oystercatchers, Hartlaub’s gulls, Kelp Gulls, and Swift terns.
In 2009, data from the Earthwatch project were used to back up recommendations made by a group of African penguin specialists to close offshore waters near penguin breeding colonies in South Africa during the breeding season. It is hoped that such measures will benefit breeding birds by increasing prey availability during the crucial chick rearing stage.
Barham, P.J., Underhill, L.G., Crawford, R.J.M., Altwegg, R., Leshoro, T.M., Bolton, D.A., Dyer, B.M. & Upfold, L. (2008a) 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. African Journal of Marine Science, 30(3): 595–602.
Barham, P.J., Underhill, L.G., Crawford, R.J.M., Altwegg, R., Leshoro, T.M., Bolton, D.A., Dyer, B.M. & Upfold, L. (2008b) The efficacy of hand-rearing penguin chicks: evidence from African Penguins (Spheniscus demersus) orphaned in the Treasure oil spill in 2000. Bird Conservation International 18: 144-152.
Barham, P.J., Underhill, L.G., Crawford, R.J.M. & Leshoro, T.M. (2007) Differences in breeding success between African penguins (Spheniscus demersus) that were and were not oiled in the MV Treasure oil-spill in 2000. Emu, 107: 7-13.