Skip to navigation | Skip to content

Wooden decoys fool passing birds

tern decoy

Tern decoys have been used all over the world, including this one off the coast of Maine (US Fish & Wildlife Service)

Conservation workers have used wooden decoys of endangered seabirds to attract the real thing to a safe breeding site on Australia's south-east coast.

They placed 50 wooden tern replicas, which were carved by a local woodworking craft society, on a sand island in Lake Wollumboola, near Culburra in New South Wales.

Less than a week later, at least eight little terns had stopped off from their annual migratory flight.

"The real test will be to see if the terns nest there but we're delighted that the decoys have done their job so far," said Michael Jarmon, a shorebird conservation officer with the NSW National Parks and Wildlife Service.

Thousands of terns once migrated each southern spring to the NSW coast to breed, but habitat loss, human disturbance and exotic predators resulted in their numbers dropping to as few as 100 breeding pairs in the late 1980s.

The species is vulnerable because it nests on sandy ground close to water. "Through a combination of fencing, volunteers, fox-baiting and pest-bird control, their numbers are now back up to about 450 breeding pairs and they have started new colonies and nesting in places where former colonies used to be," Jarmon said.

"The idea now is to try and get these birds into areas that we think are safest for them." In this case, recent rains have lifted water levels in the coastal lake enough to isolate a sand island, deterring foxes, cats and dogs.

Little over a week ago, the conservation workers set the replicas in pairs. They then created a false nesting scrape, or small hollow, in the sand in front of each pair. When Jarmon returned to the scene six days later, eight terns had already landed and were standing with the decoys.

If they and others start nesting, the decoys will be removed so not to draw too much attention from predatory birds, such as swamp harriers and ravens: "Once there's enough real terns they're perfectly capable of ganging up on a raven and driving it off."

Jarmon believes decoys work partly because birds rely so heavily on their visual sense. Migratory species, seeing decoys floating on water or perched, probably assume that area is safe from predators, he said. The birds could also think that the area provides attractive resources.

Bird hunters have long used decoys to attract birds, in what may be a technique handed down from ancient times. Australian Aborigines traditionally used decoys and camouflage to capture water birds, as did Native Americans.

The Phoebe A. Hearst Museum of Anthropology in the U.S. holds preserved organic objects taken in 1912 from Lovelock Cave, Nevada, including duck and goose decoys made from reeds and straw thought to be about 2000 years old.

Hunters have also traditionally used decoy sounds and live decoy birds, either tame or captured wild birds with their wings clipped, to attract wildfowl within range of their weapons. And wildlife agencies are increasingly experimenting with those techniques as well for conservation purposes.

In 1990 the US Navy relocated an endangered tern colony on its North Island Naval Air Station, using 900 decoys to attract the birds to a safe area set aside for them.

Birds also use physical and behavioural decoys themselves, such as faking a broken wing to lure predators away from their nests.

In Australia, the yellow-rumped thornbill is one of several species that builds a decoy false nest cup to deter cuckoos from laying their eggs in the thornnbill's real nest, hidden beneath the decoy.

Tags: environment, biology, ecology