The team: Jenny, Les, John, Kathy,                                 Offloading "the Saint" at House Bay
                   Michelle, Marienne (L to R)

The rapidly growing eco-tourism industry in the western Cape has resulted in increased pressure to open up new areas to the public. Seabird colonies represent spectacular aggregations of birds, and the offshore islands that provide protected breeding habitat are as attractive to humans as they are to birds! As part of a two-year post-doctoral study, I am attempting to quantify the effects of human disturbance on seabirds – it is essential that guidelines for approach to different species be in place before tourism is allowed in sensitive areas. I had been on Dassen Island a week previously, setting up experimental approaches to various colonies of birds. The present trip provided an opportunity to record the responses of these colonies to approaches by groups of humans. For this reason, I headed out before the rest of the group to the colony of pelicans breeding at Boom Point, set up the ADU’s video camera and began recording the birds’ behaviour. The rest of the group arrived a little later, and began a careful, gradual approach towards the colony. The reaction of the birds was quickly apparent – even at a distance of over 100m, the birds became more alert and ceased pre-approach behaviours such as grooming and the feeding of chicks. As three members of the group edged even closer, non-breeding birds on the perimeter of the colony began to fly off, while within the colony adults laboriously flapped their huge wings in alarm, and several chicks waddled off their nests. Repeated disturbances of this nature, and by people less sensitive to the effects of their approach, could have extremely deleterious consequences for this near-threatened species.

From their position near the colony, Michelle and the rest of the group observed pelicans incubating eggs and brooding downy chicks a few weeks old.  There was a high proportion of sub-adult birds roosting on the island.  However, there was no sign of birds wearing jewellery - the blue bands which were fitted to chicks earlier this year and which would have indicated a return of one-year olds to the island.

                 The colony at Boom Point                                                          Pelican Art

Towards sunset we hitched a lift with Deon, the lighthouse keeper, to the southern end of the island. Slightly out of breath, we reached the top of the lighthouse to be greeted with a glorious 3600  view of the island. John regaled us with anecdotes of previous lighthouse keepers, murder and intrigue, from the bad old guano-scraping days. As the drowsy sun sank into the gentle folds of the ocean for the night, we scanned the shore for waders – Kathy’s special interest. Later in the evening, Les and Kathy would head out to catch and band any unwary plovers that fell within the reach of their net. First, however, we relaxed in the communal kitchen or around the fire as we waited for dinner to cook and enjoyed more guano-scraping tales from John. We were also entertained with stories of the Wild West Coast by the divers who were on the island for a few days, busy with salvage of the wreck of  “the New Mexico.”

      Top of the World                    John and the Dassen Wall-Walk                    Kathy & Les scan for plovers

Early the next morning, Kathy and Les were rewarded for their persistence with the capture of six Kittlitz’s plovers. After breakfast, our group split up for a count of the waders on Dassen’s shores; Les and Kathy headed one way while John, Jenny and Michelle headed the other. Amongst the species seen were the African Black Oystercatcher (334), Blacksmith Plover (19), Common Sandpiper (1), Curlew Sandpiper (65), Grey Plover (2), Sanderling (49), Whimbrel (1) and  White-fronted Plover (84). I set off to the Bank Cormorant colony near the skeleton of “the New Mexico.” Several birds were engaged in fascinating courtship displays to attract potential mates. Just as riveting were the stylised dual displays by birds with established nest sites. Les and Kathy passed by between the camera and birds a little later, allowing me to collect data on behaviour of the birds before, during and after disturbance. A previous study at Stony Point, Betty’s Bay, had suggested the susceptibility of this endangered species to disturbance, and the present experiment supported this. Upon approach, courtship was interrupted and displaying birds flew off. Birds on the perimeter of the colony were once again most affected, including one pair that was scared off by an harassing Kelp Gull and whose nest was soon torn apart by marauding Cape Cormorants.

                  Bank Cormorant display                                    L & K passed between camera and birds

At midday on Thursday we waved goodbye to Johan and Dassen and, saluting lazy wallowing whales on the way, rode the swells back to Yzerfontein aboard “the Saint.”  The call of the islands, once awakened in the blood, is not easily silenced, and Dassen awaits our return…

                                                                        Dassen Island awaits our return

Acknowledgements

Thanks to Western Cape Nature Conservation for permission to work on Dassen Island, and to Johan Visagie for his hospitality. Also, sincere thanks to Earthwatch for sponsoring the video camera used to capture the images illustrating this article, and used in the course of the project on the effects of human disturbance on seabirds.
 
 

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Document posted 21-October-2002