Shortly before dawn on Dec. 19, Pepper Trail and Chris Uhtoff will take their positions along the side of the Rogue River's Gold Ray Dam and prepare for the greatest annual underestimation among local birders.

Shortly before dawn on Dec. 19, Pepper Trail and Chris Uhtoff will take their positions along the side of the Rogue River's Gold Ray Dam and prepare for the greatest annual underestimation among local birders.

Soon ribbons of black with hints of orange will cloak the sky, then Trail will raise his arm toward the mass and make a fist.

That fist calibrates the sky for Trail, who estimates that a fist-size view of the ribbon represents 100 American robins in formation as they dart out of their mass roosting site upstream of the dam.

"I'll put my fist up and count, say, 12 fists worth of bird and write that down," says Trail, an Ashland ornithologist. "I'll just, essentially, continue that process."

The pair likely will tally 500 fistfuls or more of robins Dec. 19 during the opening hour of the Medford area's contribution to the annual Christmas Bird Count of North America.

The local American Robin phenomenon falls to the tally of Trail and Uhtoff, chronicling one of the most incredible features witnessed during the annual count since it was first discovered here four years ago.

Hard to imagine 50,000 birds hiding that well that long.

"It's a very approximate number, of course," Trail says. "Definitely, though, the numbers we have are estimates."

Estimates and exact counts of avian phenomenons will occur throughout the country as the National Audubon Society oversees its 110th annual exercise in "citizen science," documenting birds present on a given day from sunrise to sunset.

It runs from Monday through Jan. 5.

The survey takes place within "count circles" that are focused on specific areas and organized by a count compiler.

The circles encompass all the area within a 7.5-mile radius from a specific point. In Medford, that's the intersection of Highways 62 and 140.

The data are compiled and shared nationally for a snapshot of what's present and visible on count day. The long-term data set can help show trends in abundance and distribution of species.

This version of so-called "citizen science" — using amateurs to capture data for scientists and other specialists — has the longest history in ornithology, says Bruce Dugger, the Mace Professor of Watchable Wildlife at Oregon State University.

For more than a century, groups of volunteers all across the continent have provided information on the distribution and abundance of their local birds during the winter, Dugger says.

Most counts are of individual birds or small aggregates, but flock counting becomes the macro version of the exercise.

It's not unusual, for instance, to see tens of thousands of migrating geese congregating in open water at places like the Tule Lake National Wildlife Refuge south of Klamath Falls.

But rarely do vast clusters of robins such as that experienced upstream of Gold Ray Dam pop up during Christmas counts, says Dugger, whose OSU position was endowed by former Central Point resident Bob Mace, who coined the term "Watchable Wildlife."

"That's a fairly significant number of birds," Dugger says. "That's pretty cool. It must be a real interesting spectacle to witness."

The spectacle has its roots as much in robin behavior as it does in their adopted winter resting place.

Seeing large numbers of wintering robins here is no strange feat. Along with year-long valley residents, the Rogue Valley often becomes a winter home for many thousands of robins migrating south from Alaska, usually reaching here around Halloween.

They are not true flock birds, but their large aggregations serve two clear purposes, says Trail, an ornithologist at the U.S. Fish and Wildlife Service's National Forensic Laboratory in Ashland.

First, night roosting together offers better protection from predators such as hawks — for no other reason than the odds are in a robin's favor, Trail says.

"If you're in a group of 1,000, the chances of you getting eaten is less than if you're alone," he says.

When together, robins share information about good places to find food, such as madrone berries, he says.

The flock grows as individual or small groups of birds notice the convoy-like collection of their brethren and simply join in.

But why the backwaters of Gold Ray Dam?

"The place itself has the character to make it a good roost," Trail says.

The backwater is home to great clusters of old, large cottonwoods that can support plenty of birds, Trail says. And it is isolated enough to prevent evening disturbance, he says.

But perhaps most importantly, the impounded water beneath the cottonwoods soaks up enough sunlight during the day to act as a night-long radiator during cold winter nights, he says.

"It's definitely a good place to be," Trail says.

Though the robins likely trickle to the roost in groups during the evening, they tend to dart out together for 30 minutes or so around dawn, likely heading to the nearby madrone forests.

"It's because they're hungry," Trail says.

This year's robin count could be the last one during which Trail and Uhtoff will launch their canoe in the Kelley Slough area upstream of the dam.

The 105-year-old dam is scheduled for removal next summer, should an Environmental Assessment now in the works point to removal as the best environmental and financial solution for its owner, Jackson County.

Trail, however, does not believe the dam's removal would threaten the roost. Punching a road near the roost site would be more troubling to the robins, regardless of the dam's status, he says.

Likely a bigger threat are the overgrown thickets of Himalayan blackberries that prevent new cottonwoods from sprouting to replace the current ones when they die, Trail says. And they will eventually die, he says.

"Even if the roost were to be lost, I doubt it would make an impact on the valley-wide population of robins," Trail says. They'd have to find another roost."

Then another duo will have to discover the robins' new winter haunts during a future Christmas Bird Count.

Reach reporter Mark Freeman at 776-4470, or e-mail