The main working tools of a bird biologist used to be a good pair of binoculars and a sturdy set of gum boots. But some biologists are now spending most of their time in front of a computer screen, downloading the type of information that they could only have dreamed of obtaining even a decade ago.

Satellite telemetry is revolutionizing bird research, particularly work on migrating species. These birds cover such huge distances so quickly that it is very difficult for earth-bound humans to track their progress.

But now hundreds of birds around the world are packing along tiny transmitters that transmit information to orbiting satellites. When this information is relayed back to stations on earth, researchers can track the progress of birds as they migrate, even for many thousands of kilometres.

The transmitters can pinpoint not only the bird's location, but also its speed. For example Tundra Swans migrating through the Yukon were clocked at ground speeds ranging from 60 to 90 kilometres per hour.

Many of these research projects have their own web pages, providing a bonanza for bird-watchers as well as researchers. Log onto the Internet now and you can follow the progress of Sir Syd, a Tundra Swan migrating between his winter home in North Carolina and breeding ground in the Mackenzie Delta. Or you could track Crane 20836, a Sandhill Crane that migrates through the Yukon.

Other web pages show the flight paths of Peregrine Falcons migrating between Central America and Alaska, Surf Scoters that regularly touch down in the Yukon, Northern Pintail Ducks, Ospreys and a host of other species.

The use of transmitters for studying wildlife is not new as researchers have been putting radio collars on various animals since the 1950s. But radio telemetry has its limits as researchers usually rely on flying over the animals in a plane equipped with special antennae to pick up signals from the radio transmitters.

In the late 1970s the development of sophisticated satellite transmitters meant that researchers could use orbiting satellites to collect data. These early transmitters were relatively bulky so they were only used on large mammals like bears and caribou.

Transmitters should weigh only three to five percent of an animal's total weight, and only in the last decade has it been possible to make devices small enough to track birds. The first project dates back to 1990 when satellite telemetry was used to study an endangered population of Siberian Cranes.

Now there are transmitters tiny enough to track species as small as Sandpipers. Some transmitters are fixed to custom-designed harnesses that are strapped around the bird's body. In other cases tiny transmitters have been surgically implanted in the bird's abdominal cavity.

Concerns do exist about how these transmitters affect the birds carrying them. In an Alaskan study of Surf Scoters, transmitters were implanted in ten birds and five had died within 19 days of their release. The researchers speculated that the weight of the transmitters could have made the scoters an easier target for predators such as eagles.

The trade-off is that satellite telemetry can provide invaluable information that can help to protect species. Researchers usually concentrate on areas where birds congregate, such as breeding areas and wintering areas. Figuring out migration routes tends to be a case of connect-the-dots, as often scientists do not know what route the birds follow from one place to another.

Jim Hawkings, a biologist with the Canadian Wildlife Service, says that Trumpeter Swans are a case in point. "We now that swans from Alaska go through here but we do not know the exact link between the breeding and wintering areas. We do not really know where they stop along the way," he says.

"All the data from conventional bird banding is concentrated in areas where people shoot birds," Hawkings explains. "Swans are not hunted in most areas, so we do not get much information that way. So there are a lot of gaps in the data."

Using satellite telemetry could fill in those gaps, leading to protection -- or better management -- of important resting areas along the birds' migration routes. With some species, researchers hope that better information might aid in helping to reverse serious declines in their populations.

Populations of Pintail Ducks, for example, have plummeted over the last 30 years. Intensive efforts are now underway to protect this species, and identifying spring migration routes and critical staging areas through the use of satellite telemetry is seen as an important first step.

The pintail project uses the Argos telemetry system, which has receivers on board satellites from the National Oceanic and Atmospheric Administration (NOAA). The pintail data is first relayed to NASA's Goddard Space Flight Center, and then on to the computer terminals of wildlife researchers around the globe.

The information is also available very quickly. Carol McIntyre, a researcher in Denali National Park, is using satellite telemetry to study Golden Eagles that breed in the park. She says that the information is sent on to her so fast that "it is practically like real-time tracking."

During the last three years McIntyre and her colleagues have placed about 50 satellite transmitters on Golden Eagles in order to locate their migration routes and wintering areas. The eagles winter in areas like the Front Range of the Rocky Mountains in Colorado where development is altering the habitat very quickly.

McIntyre hopes that the information they are gaining will led to better management of the eagles' habitat. And she says that satellite telemetry is the only way to get this sort of data.

"I tend to think of it as a technology that helps us answer questions," she says. "We would never have been able to get this much information in 50 years working without it."

The following web sites have information on satellite telemetry and birds:

• Argos satellite system
• Peregine falcons
• Sandhill cranes
• Pintail Ducks
• Tundra Swans (including Sir Syd)
• Satellite Tracking of Threatened Species