Sometimes shoals of bait fish can be seen from the shore of the Gold Coast, their presence is often indicated by congregations of seabirds, some of which nosedive dramatically from a great height into the midst of the schooling fish.
Most of these plunge divers are usually Australasian Gannets. These are a handsome white streamlined seabird with an apricot head, long black marked pointed wings and tail, dagger shaped beak and blue eyes. They are regularly seen offshore in SEQ from April to September. They are pelagic birds which breed in colonies in southern Australia and New Zealand. The birds pair for life and return to the same nesting site, they may be quite long lived with lifespans of 30-40 years.
The hunting technique of gannets is to locate shoals of fish with its keen binocular vision, soar above to heights up to 50 metres, open its wings and dive, at the last moment the bird folds its wings back to enter the water like an arrow. The bird may hit the water at speeds of 100 kmph, its momentum can carry it 10 metres underwater. If it has to pursue prey deeper it must use its wings and webbed feet to swim downwards, it can reach a depth of 25 metres. Gannets grab a fish with their serrated bills and usually swallow their prey underwater.
This spectacular hunting technique is a high energy activity and presents a number of challenges – the bird must overcome a sudden change in atmospheric pressure, positive buoyancy, the crunching impact of hitting the water at great speed and the transition from air to an aquatic environment.
Air sacs on their face and chest, super strong honey combed bone structure, extra bone in the roof of the mouth and closed nostrils are adaptations to cope with the shock of its high impact water entry. The bird’s aerodynamic shape and agility ensure that it scythes through the water at speed to maintain its momentum.
Unfortunately seabirds all over the world are threatened by human activity. Along the coast of SEQ, fishing and plastic litter pose a threat to gannets. Lures and fish hooks can be swallowed and cause ripping internal injuries, embedded hooks cause damage, pain and infection, fishing line cuts off blood circulation resulting in gangrene. Recreational fishers can prevent these accidents by not setting unattended lines, not casting in the vicinity of seabirds, correctly disposing of fishing tackle and litter and using steel rather than stainless steel or alloy hooks. If you hook a seabird don’t cut the line, reel it in gently and call wildlife rescue. Pick up discarded fishing line or plastic on the foreshore, it will only take you a minute and you may have saved many animals from a long and painful death. If you see injured or entangled wildlife call the RSPCA on 1300 852 188.