|Avian Demography Unit
Department of Statistical Sciences
University of Cape Town
Brief report on resightings of flipper-banded African Penguins at the Boulders penguin colony
This report summarizes the information on flipper-banded African Penguins Spheniscus demersus which have been resighted at the colony at the Boulders. Part of the information in this report has summarized by Crawford et al. (submitted). A more detailed analysis, which will contain the full histories of each penguin resighted at the Boulders as an appendix, is in preparation.
Up until August 1999, there were 198 records of African Penguins moving to or from the Boulders and other localities. Eleven of these related to birds banded at the Boulders and being seen elsewhere. 187 had been banded or released at other colonies and subsequently sighted at the Boulders.
Of these 187, 16 were banded by the Southern African National Foundation for the Conservation of Coastal Birds (SANCCOB), all but one having been victims of oil pollution, but their colonies of origin are not known. These penguins arrived via or continued on to other penguin colonies. Five subsequently settled to breed at Dassen Island and one at Robben Island, while another bird bred at the Boulders after spending several years at Robben Island. One had previously been recorded at Bird Island, Algoa Bay after its release from Robben Island, while another had a week-old chick on Dyer Island, five months prior to its sighting at the Boulders. Two other birds continued on their travels from the Boulders to Bird Island, Lambertís Bay and Dyer Island respectively. One oil spill victim moulted at the Boulders before being seen at Robben Island. Four other survivors from oil spills moved to Dassen Island after being resighted at the Boulders.
Nineteen African Penguins were recorded at the Boulders having been banded in adult plumage at other breeding colonies. However, their true colony of origin remains uncertain because the breeding status of birds at banding was not always known or recorded on banding schedules. A bird banded at Bird Island, Algoa Bay was found sick at the Boulders five years and eight months later, having been seen 10 days previously at Dyer Island. It subsequently died. Two were banded at Dyer Island, one subsequently breeding at the Boulders. Three were banded at Stony Point, one later breeding at the Boulders, one was banded at nearby Seal Island in False Bay, and 10 at Robben Island, one of which subsequently bred at the Boulders. Two birds made the journey from Namibia, one from Possession Island, c. 900 km away, and one from Mercury Island, a distance of just over 1000 km. Of four birds banded as adults at Boulders, one moulted at Dassen Island, while three were seen at Robben Island, one of which was moulting.
Perhaps the most interesting information comes from the birds banded as chicks, because their ages and colonies of origin are both known. A total of 142 chicks, banded at colonies other than the Boulders, was subsequently recorded visiting or settling at the Boulders colony (Table 1). Seventy-eight of these were two years old or younger when first seen at Boulders. It is known that African Penguin chicks range widely after fledging (Randall et al. 1987). Normally they return to their natal colony prior to their first attempts to breed (Randall et al. 1987). Of the 78 chicks recorded within two years of banding, 42 were not seen again after being seen at the Boulders. Eighteen were later recorded back at their natal colonies, including one bird that returned to Ichaboe Island, Namibia, a round trip of almost 2000 km. A further two penguins were found sick, injured or oiled and six were recovered dead. A chick that had been banded at Bird Island, Algoa Bay, was later recorded at Dassen Island and another, banded at Seal Island in False Bay, was later seen at Stony Point. Of those that were banded at Dassen Island, two were later seen at Robben Island, one at Ichaboe Island and eight returned to Dassen Island. Of the nine birds banded at Dyer Island, three were known to have returned there. Six of the 22 penguins banded at Robben Island returned there after appearing at Boulders, one was later recorded at Seal Island (False Bay) and one was subsequently found injured at Camps Bay.
Table 1. Colony of origin of birds banded as chicks later recorded alive at Boulders
Twenty-one of the chicks under two years of age came from colonies to the east of the Boulders while 51 had come from a northerly direction.
In addition, 64 birds banded as chicks were seen at the Boulders when aged two years or older. Twenty-nine of these were not seen subsequently and 18 are known to have returned to their natal colony. Three were found sick, injured or oiled and three were found dead. An indication of their natal colonies is given in Table 1. Twenty-eight came from an easterly direction while 33 arrived from further north. The birds from Bird Island, Algoa Bay, were found injured or dead. Three of the Dyer Island and one of the Stony Point birds are known to have returned to their natal colonies. Of those birds from Robben Island, eight were later seen back there, one having moulted at the Boulders. Six of the Dassen Island birds later returned and one of the Ichaboe Island birds seemed to be on its way back, being reported both from Dassen Island and Bird Island, Lambertís Bay. A chick hatched at the Boulders that had been hand reared at SANCCOB was seen moulting at Dassen Island before returning to the Boulders.
Banding of African Penguin chicks also gives an indication of where breeding birds at the Boulders originally came from. Seven chicks fledged from other colonies were found to be breeding at the Boulders (Table 2) and a further five may be settling there, though they have not as yet been confirmed as breeders. The natal colonies of these twelve birds were Dyer Island (6), Seal Island, False Bay (1), Robben Island (3), Stony Point(1) and Dassen Island (1).
Table 2. Chicks banded at other colonies recorded breeding at the Boulders
Seven birds banded as juveniles (i.e. post-fledging) were later recorded at the Boulders colony. All had been rehabilitated by SANCCOB, six having been oil spill victims. One was breeding at the Boulders, one had previously been seen at Bird Island, Algoa Bay, and one was subsequently recorded at Dyer Island. Three more were later seen at Dassen Island, one having been oiled for the second time at the Boulders. Two birds of unknown age, both rehabilitated by SANCCOB, were later seen at the Boulders. One, a breeding bird from Dyer Island, was found dead. Another bird, found stranded on a beach in KwaZulu-Natal was later released at Cape Receife, Eastern Cape Province, and was found injured at the Boulders. It was taken to SANCCOB and later released again at the Boulders.
From sightings of banded birds, it is apparent that the Boulders forms an important "stopping off" point for wandering young birds and for rehabilitated birds following their release. Other movements of birds to the colony probably relate to birds coming in to forage. An adult fitted with a satellite transmitter in 1996, which had two large chicks in a nest on Dassen Island, spent a night at the Boulders before returning to Dassen Island to feed its chicks (Crawford & Whittington 1997).
Based on observations made between 1952 and 1984, Randall et al. (1987) considered that African Penguin chicks normally move in a westerly or northerly direction from their natal colonies. However, 49 of the chicks arriving at the Boulders, were banded at colonies to the east and 84 from colonies to the north. Randall et al. (1987) found that overall, 88% of penguin chicks from Western Cape islands moved in a northerly direction, 12% having presumably moved southwards or eastwards. In this example, 63% of birds from these colonies moved southwards to the Boulders, although some later moved north again. The explanation for this change over time is not clear, although it should be noted that the observations used in the analysis by Randall et al. (1987), were made prior to the discovery of a breeding colony at the Boulders in 1985.
The small sample of banded birds breeding at the Boulders, which have emigrated from other colonies, suggests that 71% could have come from Dyer Island. The latter colony has declined by 90% during the growth period of the Boulders colony, and this decline is thought to be related to a shift in the prey regime (Crawford 1998). However, it should also be noted that single birds from Robben and Dassen Islands, both also showing an increase in numbers, have relocated to the Boulders. The ages of chicks from other colonies settling to breed at the Boulders, ranged from three and a half years to just over seven years. It is possible that the first attempt at breeding by some of these birds was missed, but none were known to have attempted breeding at their natal colony. It would appear that chicks under two years old recorded at the colony were most likely to be transient wandering individuals, whereas those over three years old were potential immigrants to the colony. Of chicks banded at other colonies that were older than two years when first seen at the Boulders, 34% had come from Dyer Island , whereas the proportion of birds from Dyer Island seen at the Boulders when two years old or younger was 13%.
Very few penguins have been flipper-banded at the Boulders. Consequently, little is known about the dispersal patterns of the birds breeding there. It would be a good investment to ring approximately 100 adults and chicks per year in order to follow their movements. It would also be worthwhile to monitor flipper-banded birds at the Boulders with greater intensity. We know little about patterns of visits by penguins to colonies other than their own. The Boulders is probably the only colony where a regular watch for banded birds is feasible, and where it will be possibly to find out the lengths and frequencies of visits to colonies.
BP Southern Africa, the International Fund for Animal Welfare, and the Chicago Zoological Society, Brookfield, Illinois are gratefully acknowledged for their support of penguin monitoring by the Avian Demography Unit. I would like to thank the staff and volunteers of Cape Peninsula National Park, staff of Marine and Coastal management, B. Barham and P. J. Barham for kindly making available their sightings of banded penguins.
Crawford, R.J.M. 1998. Responses of African Penguins to regime changes of sardine and anchovy in the Benguela system. South African Journal of Marine Science 19: 355-364.
Crawford, R.J.M., Shannon, L.J., Whittington P.A. & Murison, G. submitted. Factors influencing growth of the African penguin colony at Boulders, South Africa, 1985-1999. South African Journal of Marine Science.
Crawford, R.J.M. and Whittington, P.A. 1997. Jackass Penguin Spheniscus demersus. In: Harrison, J.A., Allan, D.G., Underhill, L.G., Herremans, M., Tree, A.J., Parker, V. & Brown, C.J. (Eds). The atlas of southern African birds. Vol 1. Non-passerines. BirdLife South Africa: Johannesburg: 4-5.
Randall, R.M., Randall, B.M., Cooper, J., La Cock, G.D. and Ross, G.J.B. 1987. Jackass Penguin Spheniscus demersus movements, inter-island visits, and settlement. Journal of Field Ornithology 58: 445-455.