Lake Illawarra is shallow coastal lagoon just to the south of Sydney. A wonderful spot for waterbirds, I stopped near the lake entrance to stretch my legs and see what wildlife was around.
There is a series of rock groynes near the entrance to the lake. Groynes are designed to stabilise the shoreline by capturing sand as it sweeps past in the tide. They stick out twenty to thirty metres perpendicular to the shore. Groynes are great places for roosting waterbirds, with water on three sides and difficult access from the shore. A lone Darter was resting on one of the groynes. The darter’s colours were a bit patchy, maybe moulting from its juvenile to adult male plumage.
The tide was running hard and creating swirling eddies off the ends of the groynes. There were patches of quiet water in the lee of each groyne, and swimming in one was a Little Pied Cormorant. I watched it disappear beneath the water and stay under for more than 30 seconds. When it boobed to the surface it had a fish in its beak. A quick flick orientated the fish head first, then down the hatch and back underwater. The cormorant went through the same cycle half a dozen times, emerging each time with yet another fish.
I was surprised at the cormorant’s success. Thinking about that quiet patch I decided that the eddy must have trapped one of the large schools of Southern Glassfish that often aggregate at the entrance to estuaries. Moving closer and reviewing the resultant image, I realised that the next fish wasn’t a glassfish, which look a bit like a small anchovy or pilchard, but a local scorpianfish known as Fortescue. The next few dives showed that this was no anomaly, with the cormorant catching nothing but the small scorpianfish.
So, no school of glassfish, instead an abundance of spikey Fortescues. Fortescues are one of the Scorpianfishes, so named because of their venomous dorsal spines. Fortescues can deliver an extremely painful sting and are cursed for their habit of getting tangled in prawn and crab nets. They are ambush predators that spend their time on the seabed. Fortescue often form large aggregations, and seem fond of clustering around Wobbegong Sharks. The Fortescue’s abundance and habit of living in large groups explained the cormorant’s hunting success, however I was amazed that it was so untroubled by the Fortescue’s venomous defences. Definitely food to be swallowed head first!
Further along the shore a Great Egret stalked the shallows. They usually spook if you approach too closely, so I circled ahead so that it was walking towards me. The egret’s head darted forward under the water, emerging with a long and energetically thrashing prey. Again my thought went to the ‘palatable’ option, a juvenile eel or elver. The egret continued forward, and another plunge resulted in another wriggly item of prey. Reviewing the image on my camera, I saw that it wasn’t an eel, but a pipefish.
Pipefish are a relative of the seahorses and seadragons. They are slow moving, relying upon camouflage and armour of interlocking plates for protection. Another spikey food item, and not a species I would have thought offered much in the way of food value. One of the images showed the egret covering its eye with a protective membrane as it swallow the pipefish.
Lake Illawarra is full of the types of fish and crustaceans that attract human anglers, species like bream, whiting, prawns and blue swimmer crabs. My half hour walk along the lake’s edge provided a gentle reminder that our preferences in the seafood stakes aren’t necessarily what attract wildlife such as cormorants and egrets. Spikey definitely has its’ place on the menu!
Later in the weekend I was delighted to see a species that was once rare around Sydney but is becoming increasingly common, the Pacific Baza or Crested Hawk. Walking in the Lane Cove valley I was startled by a magpie sized raptor crashing into the foliage a few metres away. The baza hung from the leaves before gulped its prey. It heaved itself out of the tangle of foliage and flew up to a nearby branch. Pacific Bazas are a specialist in another form of spikey food, in this case stick insects. I watched it swoop into the foliage a few times without managing to actually see the prey item. A surprisingly modest diet for such an impressive raptor.
Most of my weekly posts revolve around a topic or theme. Each week I tend to find one or two that don’t fit the topic but are still worth sharing. Future posts will feature an ‘odds and sods of the week’ section, no text, just images.
Odds and sods of the week