ADU travels, expeditions and events

The Islands of Saldanha Bay and Langebaan Lagoon:
A Trip in Time

Marienne de Villiers, Janine le Roux & Michelle du Toit

Islands carpeted with birds (M. du Toit)

It was a trip that would have done Lawrence Green proud. That historian, explorer and prolific writer with a soft spot for isolated places with quixotic stories would have appreciated this adventure: a trip back in time to the days of shipwrecks, guano-scrapers and islands carpeted with birds.

The transport and the motivation for this trip were thoroughly modern, however. On the 19^th of February, we boarded Marine and Coastal Management’s research vessel, the Sardinops.

The Sardinops at sunrise (M. du Toit)

The aim of the six-day trip was to add to MCM’s steadily growing information-base on those seabirds breeding on the eight islands of Saldanha Bay and Langebaan Lagoon.

In 1658, four men were allowed to settle at Saldanha Bay as fishermen and, within a fortnight, they had secured their first cargo of fish, salted penguins and thousands of penguin eggs. This was the beginning of the almost manic exploitation of the islands for their natural wealth. Before long, however, seabird numbers began to plummet.

Today, seabird colonies are threatened from a number of directions. Commercial fisheries exploit many of the same fish species that the birds rely upon for food, marine pollution is an increasing problem, and the disturbances associated with tourism and other

Marine pollution: an oiled Gannet (M. du Toit)

human activities may cause birds to desert eggs, chicks, or even entire breeding sites. Seabirds have natural predators too: seals sometimes supplement their diet of fish by preying on birds resting on the sea surface, and pelicans prey on the chicks of other bird species.

On board the Sardinops were her Captain and crew, Bruce Dyer and Leshia Upfold of MCM, and Janine le Roux, Michelle du Toit and Marienne de Villiers of the ADU. After four hours of steaming up the coast on a calm and sunny sea, we stopped off briefly at Dassen Island. Here, Janine and Leshia were met by Johan Visgie, warden of the island. The Sardinops continued on to Vondeling Island, taking advantage of the good weather to make one of the more difficult island landings. Bruce, Michelle and Marienne hopped off the rubber duck onto the large boulders near the island’s broken jetty and cautiously made our way to shore, trying to minimize the disturbance to those Cape and Crowned Cormorants nesting in the vicinity.

View of the Sardinops from Vondeling Island

Guano stalagmite (M. du Toit)

Our first task was to check the abandoned buildings, dating back to guano scraping days, for nesting birds. Stalagmites of guano creeping up door and window frames testified to the Cape Cormorants nesting under the eaves, and several penguins had made themselves at home in the cool, dusty darkness of the buildings. One enterprising pair had selected an old coal stove as the nursery for its anticipated offspring. Finished with the buildings, we split up and quickly counted those birds – mostly Cape Cormorants and African Penguins - nesting inside, on top of and outside the wall erected by the guano scrapers to make easier their task. With a good afternoon’s work behind us, we were ferried back to Dassen Island where we would spend the next few nights.

Dassen Island (about half the size of Robben Island and the biggest of the group we were to visit) was presumably named for the rabbits which were introduced as an alternative food source for the guano scraping teams, and which proceeded to live up to their name and “breed like rabbits.” On the island, we split up to each pursue our own particular interest. Leshia and Johan began their bi-monthly count of moulting  penguins, as well as tallying the numbers of various other species around the island. Bruce buried himself in paperwork, while Marienne spent several entertaining hours observing and filming Bank Cormorant behaviour. Meanwhile, Michelle helped Janine with her MSc project on Swift Terns. Janine takes up the story.

Marienne, Janine and Bruce, on Dassen Island (M. du Toit)

Bank Cormorant coming in to land by its partially albanistic mate (M. de Villiers)

Janine:

Nesting Swift Terns (M. du Toit)

My top priority for this field trip was to ring the Swift Tern chicks that were observed on our last trip to Dassen Island (28 January 2002).  Dassen Island has been a popular breeding site for the Swift Terns, due to low levels of disturbance and few predators. This meant it would be the perfect place to ring chicks with my recently received Pro-Touch Engraved bands. My aim was to ring at least 500 chicks, so that once they fledged I would be able to monitor their movement via a re-sighting program.

After being dropped off at Dassen Island, and leaving the rest of the researchers to go to Vondeling Island, it was decided that the day was much too hot to start ringing chicks and subjecting them to that heat stress.  So we would start first thing the next day before it got too hot.

The next morning I woke up early, jumped out of bed, full of excitement about the chance to finally ring some Swift Tern chicks.

Great White Pelicans: the “Baddies” (M. du Toit)

It was then that the bad news came  - the pelicans had eaten all the Swift Tern chicks!  All three colonies of breeding Swift Tern had been decimated and used as another food source for the Great White Pelicans living on Dassen Island! (Being a scientist in training I realise I will have to eventually accept this as the normal course of events in the natural world.)

I stayed on Dassen Island for the rest of the week and was able to spend quality time observing the behaviour of the Swift Terns as they prepared to start with their next breeding attempt. I felt really privileged to be able to spend that time on Dassen Island, I had a room over-looking the penguin colony and even got used to the two mice living in my room. With the variety of seabirds that breed and roost on Dassen, it will definitely be worth a visit by all keen birders once or if the island is open to tourism.

In-between all the hard work, we sought relief from the heat by diving off the island’s jetty – out of the frying pan and into the freezer! In the late afternoons, as the sun was going down, we snatched some penguins on their way back from the sea and relieved them of their recently hard-won meals, all in the name of Science. Although in the short term this was undoubtedly unpleasant for the few birds thus bothered, the information gleaned regarding the state of the pelagic fish stocks on which penguins rely, will contribute to the conservation of the species.

From left to right: Leshia, Bruce and Michelle, relieving a penguin of its meal (M. de Villiers)

After two days on Dassen Island, Bruce, Michelle and Marienne moved base to Malgas Island, named after the thousands of Cape Gannets (“malgasse” or “mad geese”) that call it home. In August 1844, 300 ships lay at anchor around Malgas while men were “digging, fighting and dying for the sake of the “white gold” left by the gannets”. Now, thankfully, the only human activity on the island is the weekly swap-over of a single Nature Conservation official who guards the island and its resources against poaching. On Malgas Island, the numbers of breeding African Black Oystercatchers and Cape, Crowned and Bank Cormorants were tallied. As for the penguins on Dassen Island, each evening diet samples were taken from several adult gannets. We also recorded the density of gannet nests in quadrats of a pre-determined size. This information, together with aerial photographs taken earlier in the year, would assist in estimating current gannet numbers on the island. Walking through the densely packed birds in order to count them was simply NOT an option!

Gannets at Malgas: here, birds have right of way (M. du Toit)

Walking through the densely packed birds was not an option (M. du Toit)

Malgas Island is one location at which repeated predation by seals on gannets has been observed. During our stay there, we took turns keeping a look out for such behaviour. During the few hours of observation, numerous predation events were seen. From our restricted vantage point on land, it appeared that only two or three seals were responsible for all the predation, which was especially intense when the wind dropped. Fledgling gannets, preening and cooling down on the sea surface, find it difficult to take off under such conditions, making them “sitting ducks” for the submarine predators. Often,

A fledgling gannet with fatal injuries inflicted by a seal (M. du Toit)

the seals would feed on the carcasses of the birds they had killed. Just as often, however, they would merely injure the bird, leaving it to flounder its way back to shore with fatal injuries.

In between the work on Malgas Island, counting trips were taken to several other islands. The one that stood out (both literally and figuratively) was Jutten Island. This little island, with its natural kopjes and numerous walls and stone stacks erected to facilitate the harvesting of guano, hides the graves of the crew of the Merestyn. The vessel ran aground one night in 1722, when she put into Saldanha Bay in search of fresh provisions at the start of a voyage to the Dutch East Indies. Her money chests sank with her, and only a handful of ducatoons was recovered by English salvage divers 26 years later. For us, one of the highlights of Jutten was the discovery of a breeding colony of Swift Terns in a small stone enclosure near the landing stage.  The report of several hundred terns, with a few Hartlaub’s Gulls on the periphery of their colony, was guaranteed to lift Janine’s spirits after her initial disappointment on Dassen Island.

Jutten Island (M. du Toit)

Swift Terns in the enclosure on Jutten Island (M. du Toit)

To round off the bird count, Bruce and Michelle visited the islands of Langebaan Lagoon: Meeu, Caspian and Schaapen. Yet another wreck, the Bruydegom, lies in a watery grave between Meeu and Schaapen Islands. The latter island has earned itself a place in history for the distinction of being home to a lion at one time! Apparently, this beast escaped its would-be hunters on the mainland and swam to safety on Schaapen Island, where it caused the demise of a number of sheep before moving on. No lions threatened our present-day intrepid ornithologists, however. Instead, during their counts, they stumbled upon the only clutch of Crowned Cormorants which had survived the recent Pelican depradation. A less appealing sight was one that highlighted the threat of pollution to seabirds – a cormorant still entangled in fishing line, the cause of its death.

Survivors (M. du Toit)

Cape Cormorant intangled in fishing line (M. du Toit)

Back on Malgas Island, our spirits were low as the time of departure drew near and we had not yet spotted the mythical Australian Gannet seen breeding there in previous years. Each morning and evening we scanned its previous haunts, in the hopes of hearing its distinctive cry, but to no avail. Finally early on Sunday morning, just before Sardinops was due to collect us, we made one last search attempt. As we neared “the spot”, Bruce’s ears pricked up and his eyes began to sparkle. Yes, there it was! For all but keen twitchers, the bird might have been a grave disappointment, being somewhat dull compared to our handsome southern African variety. However, we left the island with gladdened hearts and one more notch to our birding belts. The trip back to Cape Town saw a continuation of the glorious weather we had been experiencing all week. Just as spirits were starting to dip at the thought of traffic jams, queues and commitments back at the office, two humpback whales surfaced close to the boat and reminded us of how lucky we are!

“How lucky we are!” (M. du Toit)

Reference:

Green, Lawrence G. 1950. At Daybreak for the Isles. Howard B. Timmins Publishers, Cape Town.