Birders have been flocking to Westbrook this month to take a gander at a rarely seen goose.

The Ross’s goose, whose typical winter migration pattern starts in northern Canada and ends between California and Texas, somewhere joined a flock of Canada geese that has been feeding in fields off Stroudwater Street.

It’s easy to spot the black sheep; it’s the only white bird in the bunch.

More than 100 people who follow online birding sites where sightings are posted have made their way to Westbrook, parking their cars along the side of the street to try to get a glimpse of the goose.

“It seems like every time I look there’s someone stopped,” said Daryl Temple, owner of Stroudwater Tire & Auto located right by the fields.

Temple knew they were looking at the geese but wasn’t aware an uncommon bird among them had drawn the unusually large crowd.

SEVENTH RECORDED APPEARANCE

It’s the seventh recorded appearance of a Ross’s goose in Maine, with the first sighting in 2002, said Doug Hitchcox, staff naturalist at Maine Audubon.

Pat Moynahan, a birder from Biddeford, has found two of them, including the one in Westbrook.

Moynahan, 76, said she drives by the Stroudwater Street fields a couple of times a week in November to see the geese.

It was on one of those routine checks on Nov. 30 that she spotted the white goose among the flock.

She got out her telescope and immediately recognized the species, which she called “a nice surprise.”

Moynahan, who served in the Air Force Nurse Corps, was stationed in San Antonio, Texas, where Ross’s geese are more common.

“It’s a sweet goose, and I invite everybody to get out and take a look at it,” Moynahan said, though she warned to be careful of the traffic on Stroudwater Street.

The high-profile location might be a reason this bird is getting a lot of attention, Hitchcox said.

When Bob Dewire of Stonington, Connecticut, was planning a birding trip through northern New England this week, he was excited to see posts online that a Ross’s goose was in the area and hanging out in a field that he had visited before.

“We knew right where to go,” said Dewire, who was traveling with his partner, Anthea Skiffington of England.

MIDMORNING TREK TO WESTBROOK

After an unsuccessful stop in search of a king eider duck reportedly seen at Biddeford Pool, they headed up to Westbrook midmorning on Wednesday.

Within 20 minutes, the flock flew up into the air for them to see.

“He sticks out like a sore thumb, so it was pretty easy to see him,” Dewire said of the Ross’s goose.

He had seen the species before, but never in Maine.

“It was great,” he said. “It’s an event for someone who’s interested in birds like we are. It makes the day.”

Hitchcox guesses the geese will remain there until there’s snow on the ground, when they’ll head south.

Although the Ross’s goose might take off as soon as it’s gotten enough fat, he said, his hunch is that it will stay with the same flock for the winter before making its way back to where it came from.

Hitchcox speculated that the bird may have gotten mixed up with a flock of snow geese, which look similar to the smaller Ross’s goose, before joining the Canada geese it’s with now.

But, whether it was pulled by a strong wind or feeding with the wrong flock, there’s no way to tell how it got off track.

“That’s one of the most fun things about birding,” he said. “Who knows how it got here?”