A Tern-up for the books!

Those with eagle-eyes out there may have noticed an unusual bird feeding in the Prawn Rock Channel; a Common Gull-billed Tern has decided to visit the Wilson Inlet. It is rarely seen on the South Coast and this is the first time it has been recorded on the Inlet since 2001. It is more usually seen in the north of the state, notably in Roebuck Bay, near Broome. The Common Gull-billed Tern is a little smaller in size to the Crested Terns seen roosting on the sand spit north of the bar, however, as its name implies, it is more gull-like with an overall white appearance, a shorter, more robust, black bill, black legs and broader wings, the bird is in its non-breeding plumage with a grey cap and dark patch behind its eye. It feeds by flying close to the water, often along the edge of the algal areas around the island, occasionally dipping its bill into the water to catch small fish or invertebrates.

We generally see three or four species of terns at the mouth of the inlet; all are white below and silver-grey above and have black caps when in breeding plumage. The smallest of these is the diminutive, yellow and black billed Fairy Tern. The Fairy Tern once used to breed at the mouth of the inlet, but there has not been any recorded breeding here since 2011. They breed in colonies often near the water’s edge, with individual nests comprising only of a “scrape” in the sand sometimes with small pebbles or fragments of shells. Usually one egg is laid which takes 3 weeks to incubate; the downy chicks take a further 3 weeks to fledge and are able to fly.

During the whole 6-week breeding cycle the eggs / chicks are extremely vulnerable to predation from feral cats, foxes and raptors, eggs can also become unviable if the birds are disturbed during incubation, which also increases the risk of predation. The nests are highly cryptic and are therefore also vulnerable to accidental damage from beach “traffic”. Numbers of Fairy Terns are in decline as a result of these impacts on breeding and the Federal and State legislation lists the Fairy Tern as “Vulnerable”.

Last year there were 30 Fairy Terns on the spit and courtship rituals were observed such as male birds offering gifts of small fish to females. Unfortunately no breeding took place. A fence has been erected on the southern end of the spit again this year, to give the birds an area where they are not disturbed, in time it is hoped that the Fairy Terns will feel secure enough to once again breed by the Wilson Inlet.

Australian Gull-billed Tern (2019)
Fairy Terns - Courtship Ritual