For the past few weeks, ducks breeding and raising their young in the southern Yukon have been watched closely.

Automobiles pull up quietly near lakes and marshes, and the occupants climb out, carrying binoculars or telescopes and clipboards full of paper. They find a good vantage point and settle in to record what the local waterbird population is up to.

Although the whole process is probably very mysterious from a duck's point of view, there's nothing sinister about it. The observers are conducting the eighth annual Yukon Roadside Survey of breeding waterfowl.

There are continent-wide surveys of breeding waterfowl, but they are mainly based on aerial surveys, says Nancy Hughes, a wildlife technician with Environment Canada in Whitehorse. The only Yukon site included in the regular aerial surveys is Old Crow Flats.

The Yukon Roadside Survey was started in 1991 in order to get more detailed information about waterfowl populations and population trends than the one-day survey of Old Crow Flats provides. The information contributes to both local and continental pictures of the status of waterfowl.

"It feeds into the process of making hunting regulations," Hughes says. "For example, if it's noticed that a species is not breeding well anywhere, that will affect regulations about hunting it."

The Yukon Roadside Survey is carried out by people from Environment Canada, the Yukon Department of Renewable Resources, and Yukon College. In the early years of the survey, Ducks Unlimited also helped.

Almost 150 wetlands are surveyed, most of them five times each, through May and early June. The goal is to get as much information as possible about all the species that use the wetlands.

"The dabbling ducks and the diving ducks have very different time frames, so we do it over a five-week period to try to cover them all," says Hughes.

The observers record the numbers, species, age and sex of the birds on the wetland. They also note if the birds are single, in pairs, or in large groups.

If there are large groups of males of one species, that species has probably finished breeding for the year, Hughes explains. If there are large flocks of males and females mixed together, they are probably still on their way to their breeding grounds.

The observers carry maps to mark the location of the wetland and the vantage point used for observing the birds so that observations from week to week and from year to year can be as consistent as possible. They also note things like ice cover, human activity in the area, and any other factors that might affect breeding birds.

Because waterfowl migrate huge distances each year to find suitable breeding grounds, they are affected not just by local circumstances but also by conditions elsewhere in North America.

Comparing records from several years of observations helps reveal those influences, Hughes says. For example, this is a particularly dry spring on the prairies, she says, and the Yukon Roadside Survey has already found more Blue-winged Teal than usual nesting in the Yukon, possibly driven further north by the lack of prairie nesting habitat.

Since 1996, brood surveys have also been conducted on some of the wetlands. By estimating the age of the ducklings, it's possible to estimate nesting and hatching dates, times when the birds are particularly vulnerable to disturbance.

The information collected so far shows a wide variation between species in the time at which nesting starts. Some Mallard and American Wigeon start nesting in mid-May and might already have ducklings by the last roadside survey in early June. Other waterfowl, like Red-necked Grebe or Scaup, start nesting up to a month later and might not even have hatched all their young by the time of the brood survey in July.

For more information about the Yukon Roadside Survey, the brood survey, and migratory waterfowl in the Yukon, contact Environment Canada in Whitehorse.