Dive into the seabirds of the Dyer Island ecosystem

Sunday July 21st 2024 we were out on the Gansbaai waters aboard the research vessel, Lwazi, retrieving and deploying acoustic receivers. The weather was on our side, clear skies and calm seas set the perfect scene. As we tried reaching the second receiver using a hydrophone, two shy albatrosses drifted gracefully close to our boat. It was a mesmerizing sight, with the albatrosses so close that we could admire the bright white plumage, black eyebrow and the characteristic grey-yellow compound bill. It is majestic seabirds like these that also sometimes manage to steal the spotlight during the whale watching and shark cage diving tours. While whales, dolphins and sharks are undoubtedly the stars of these adventures, unexpected encounters with seabirds left a lasting impression on me.
The shy albatross is one of several species of birds that clients are lucky enough to witness on the boats, since they are almost never spotted on land. Albatross are known for their impressive wingspans, long life spans, extensive breeding seasons and loyal mating bonds. Shy albatrosses (Thalassarche cauta) are the most common albatross species seen around the boats, but I was also lucky enough to witness a black-browed albatross (Thalassarche melanophris). A third species that can sometimes be spotted is the yellow-nosed albatross (Thalassarche chlororhynchos).


Juvenile black browed albatross, notice the dark underwing in comparison to the shy albatross.

While albatross are only occasionally around the whale boats, another seabirds accompanies nearly every shark trip. Within 5 minutes of Slashfin leaving the harbour, one or more large brown birds are already soaring alongside the crew and clients. They match the vessels speed with effortless ease and sometimes, land more or less gracefully on the boat, enjoying a short taxi ride. These Brown skuas (Stercorarius antarcticus), also known as the Antarctic skua, are drawn to the chumming, hoping to snatch a tasty morsel of salmon for themselves.

For the untrained eye, the brown skua can be mistaken for the Giant petrel (Procellaria gigantea) – they’re both large, brown birds, after all. But in reality, these are quit different species. The Giant petrel boasts an impressive wingspan, which in my opinion can make it seem almost disproportionate as it soars through the air. This characteristic is shared with the albatross, and it’s no coincidence; both petrels and albatrosses belong to the same order, the Procellariiformes, also known as the tubenoses. On the bill of the Giant Petrel, two tube nostrils can be observed. Through these, they desalinate their bodies by excreting a saline fluid.

While the picture is anything but good and sharp, the ‘disproportionate’ long wings make the giant petrel identifiable.

The last seabird to look out for on the eco-tourism vessels is the Cape gannet. Even from a distance, they are easily recognizable by their wing pattern. The outer half of their wings is jet black, while the rest is a crisp white, almost as if they’ve dipped their wings in black paint. From nearby, the yellow crown, and pale blue bill are worth taking a look at. When hunting, gannets retract their wings and dive into the water at high speeds, striking the surface like feathered torpedoes to catch fish below, a sight to behold.

Cape gannet flying above the water. Even in this position, their aerodynamic shape is clear.

Cormorants, often seen along the coast, can make an appearance during the trip. Often, they are spotted flying in groups, but you’ll also find individuals swimming solo. Several species occur along the South African coast, including the Cape cormorant, White-breasted cormorant, Reed cormorant and Crowned cormorant. With the distinctive white breast of the – you guessed it – White-breasted cormorant, the small crest on the head of the Crowned cormorant, and the orange bill base of the Cape cormorant, identifying them might seem straightforward. However, one should be cautious, as juveniles of the Cape and Reed cormorants also have pale bellies, and young Crowned cormorants lack the characteristic crest. Crowned cormorants tend to have an overall darker appearance, while Reed cormorants are notable for their longer tails – traits that can be tricky to discern without another species nearby for comparison. Sometimes, habitat can offer clues to make an educated guess with the Crowned cormorant typically found in marine areas, whereas the Reed cormorant prefers freshwater environments.

A last group of species that accompanies any trip are the gulls. Gulls will flock around the back of Slashfin throughout the entire shark cage diving experience, drawn by the chumming. The larger dark winged gulls are Kelp gulls, which closely resemble the Great Black-backed gulls found in Europe. The smaller gulls with lighter wings, red legs and beak are Hartlaub’s gulls. For those familiar with African Penguin & Seabird Sanctuary, Mona – the screeching, boot-pecking bird – is a Hartlaub’s gull. Grey-headed gulls, as their name suggest, are distinguishable by their grey heads and look quite similar to Hartlaub’s gulls. While their sightings are certainly not rare, they’re less common, so they’re worth a closer look if your guide points them out – unless, of course, a Great White shark appears in the bay, in which case all eyes should be on that!

Lastly, we have the terns. While some tern species are easily recognizable by bill color or size, other require a closer examination before you can confidently identify them. Factors like time of the year, location, bill color and length, tail streamers, sharp defined or faint black bars and wing shape all play a role in distinguishing certain individuals. If you are interested in diving deeper into tern identification, I happily refer you to the following article, which has described this wonderfully: https://faansiepeacock.com/identifying-antarctic-terns/
I however, will keep it short and sweet, and focus on two easily recognizable species: the Caspian tern and the Greater Crested tern. The Caspian tern wears the typical tern color palette with its red bill with black tip and black legs, but its larger size makes it easy to spot during estuary monitoring. The Greater Crested tern has, in addition to a small crest, also a large yellow bill as a remarkable trait. Other and more similar terns that can be observed in winter are the Roseate tern, Antarctic tern and the occasional Common tern. Although the Common tern is usually a summer visitor, some immature birds can be seen present year-round, as we observed during the CWAC count – a more comprehensive bird survey compared to the weekly estuary monitoring. During the estuary monitoring, a lot of different birds can be observed such as Kingfishers, Thick-Knees and an occasional Pelican. That, however, is a whole other article to cover.

The seabirds around the boats absolutely deserve a moment in the spotlight. I hope this brief guide has shed some light on the different species that often go unnoticed amidst the excitement of whale watching and shark cage diving. If you ever find yourself unsure of which bird you’ve spotted, don’t hesitate to ask one of the guides on board. And if you’re a volunteer or intern, I highly recommend joining the weekly estuary monitoring; it’s a great opportunity to get to know the local birds even better.
So, next time you’re out on the water, don’t forget to look up every now and then – the feathered visitors bring a whole new dimension to the experience. And remember, spotting a rare bird could be just as thrilling as a Great White sighting… well, almost!

Written by Silke Bouckenooghe