Cutting Edge: Eric Dorfman

August 24, 2001

When people think of storks, most usually picture the summer influx of large white birds with bright red bills and airborne babies taking up residence on roof tops, churches and trees across Western Europe.

Many Australians share this same image even though Australia has a stork of its own: the black-necked stork, or jabiru.

When Captain Cook landed on the shores of Botany Bay in 1789, he would have seen these stately birds, 1.5m tall, towering above the other species as they looked for eels and other fish in the area that is now Sydney's International Airport. The population once reached almost to the southern tip of the continent's east coast. Because of hunting and clearing, the species has by degrees retreated up the coast and now, at the southern edge of its range, exists in only a few isolated pockets. Although still relatively abundant in Australia's far north, the jabiru appears to be continuing its decline and is recognised globally as near threatened.

Now the University of Sydney's Institute of Wildlife Research has joined the New South Wales National Parks and Wildlife Service to investigate the bird's decline.

Almost nothing is known about the jabiru, which is surprising for such a large bird. Is the jabiru sedentary or does it migrate over large distances? This information is important because the nature of environmental impact will relate directly to how far the species moves. If it is sedentary, we need think only about local impacts. But if the species moves large distances, we must consider more disparate influences. In addition, being a top predator, the black-necked stork might act as an "umbrella" species: protecting it will protect many of the other species with which it shares its environment.

To find out about the jabiru's movements, we have used satellite transmitters that send an electronic signal into space and allow us to pinpoint its source. When attached to animals, they allow us to track them from the comfort - and, in the case of animals that live with crocodiles, safety - of our offices.

Transmitters were first developed for use with large animals such as buffalo, but they are constantly shrinking in size. The battery is sometimes replaced by a tiny solar panel that extends the life and lowers the weight of the transmitter. As weight was not too much of an issue with birds as large as storks, we used comparatively heavy transmitters with enough power to last between two and three years.

With such a long transmitter life, we needed to use an attachment material that was strong enough to last and soft enough not to discomfort the birds. We used Teflon ribbon, which looks like normal cloth ribbon but is very soft and, seemingly, will never break.

We fashioned a harness, looking much like a miniature backpack, that loops around the bird's wings, crosses over the breast and comes together at the back, where the transmitter sits firmly between the bird's shoulder blades.

After months of trying, we recently captured our first bird at Territory Wildlife Park, near Darwin on Australia's north coast. In this case, the lowest technology turned out to be the best - a fish and a leg noose made of fishing line. We have attached a tag to a second bird, which is still awaiting release.

Our first bird has been wearing the tag for about a month. Because he gets a bit of a handout from staff at the wildlife park, we are waiting to compare his somewhat limited movements (always less than 20km from the spot of capture) with our second, less sociable bird. Even our first bird, however, travels almost daily in search of fish to several local wetlands.

Although it is still early in the study, we are beginning to paint a picture of the stork as somewhat sedentary. However, time will give us much more information that will help to conserve not only this species, but the host of others with which it lives.

Eric Dorfman is a research fellow at the University of Sydney's Institute of Wildlife Research, Australia.

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