By Cherry Giljam
Love it or hate it, healthy water bodies should exhibit a range of different algae as well as various floating/rooted aquatic plants. All estuarine wildlife is dependent on such plants for food (direct and indirectly) and nesting material for its survival.
The Great Crested Grebe and its favourite delicacy, the endangered Pipefish, are great examples. To a greater or lesser extent, they are both residents of Zandvlei, depending on the abundance of aquatic plants.
The Great Crested Grebe is termed an uncommon resident. It is unmistakable, with long crests when breeding and long, flattened cheek feathers. They are tailless waterbirds, feeding beneath the surface by diving, remaining submerged for 20-50 seconds. They are seldom seen on land but fly long distances at night to new waters. Breeding and non-breeding plumages differ. Small chicks are striped on the upperparts, the head stripes remaining until the bird is nearly fully grown. Chicks ride on their parents’ backs. Normally silent, pairs occur on large inland waters or estuaries bordered by low, emergent vegetation. On water, when preening, they habitually expose their white underparts. Their courtship dance is something very special to witness.
Some years ago, when the Kingfisher weed eater was out of action for the whole winter, the Marina da Gama scored the highest number of Great Crested Grebe breeding pairs in the entire country!
Way back in 2001, Clifford Dorse, the first manager of the Zandvlei Estuary Nature Reserve (ZENR), discovered the extremely rare Pipefish [Syngnathinae] in Zandvlei. They are a sub-family of small fishes, which form the family Syngnathidae together with the Seahorses (Phycodurus) and Seadragons (Phyllopteryx).
They are marine dwellers in tropical and temperate zones, their usual habitat being sheltered coral reefs or sea grass beds. Their discovery living in the pondweed (potamogeton) in our estuary was quite a revelation. Usually only 35-40cms in length, they lack strong swimming ability and are easily disturbed by human recreation and pollution. Parenting duties are the responsibility of the male. They are in high demand for pseudo-scientifc medical cures and the aquarium trade. Due to their narrow distribution they are less likely to adapt to new habitats. In 2018 when the estuary mouth was opened seasonably for the winter, creating a drop in water levels, there was suddenly a bird feeding frenzy in the pondweed. To our amazement, it was Pipefish they were feeding on.
Thanks to our visiting photographer, Wilbert Mcllmoyle, Grebes, Cormorants, Hartlaub Gulls and even Herons were photographed in evidence enjoying the feast, while cut pondweed transferred to the land also contained ‘pickings’ for Egrets and other birds.
Since then, we have occasionally witnessed Pipefish being devoured by our water birds. But following the crash of our pondweed growth in 2000, we have feared for their existence. ExCom member, Lise Carswell, captured a picture of a Grebe eating its favourite delicacy a couple of weeks ago. So, we can only hope this remarkable creature is still alive and thriving in our estuary.
Please keep us posted!