Although tourists visit Gloucester most often in summer, in winter it goes to the birds.

Bird watchers come from near and far to see loons, grebes, gannets, sea ducks, alcids and gulls who also spend the season here. Now, a visitor who hasn't appeared here in 30 years is bringing more of them to the shores of Eastern Point.

The visitors and local birdwatchers were here this holiday weekend hoping to see a rare ivory gull, a denizen of the Arctic Circle that could have come from as far as Greenland to hang out around the harbor.

The gull was first spotted about noon Saturday on the Dog Bar breakwater at Eastern Point by Jeremiah Trimble, the curatorial associate and collection manager of the ornithology collection at the Harvard University Museum of Comparative Zoology in Cambridge.

"It's very unusual, it's only been spotted about 10 other times in history in Massachusetts — this includes records going back to 19th century," said Gloucester resident Chris Leahy, a bird expert with the Massachusetts Audubon Society. "It doesn't even occur annually, so it's a big deal. People will be coming from all over and our state to try and see it."

Leahy said the most recent sighting of an ivory gull on Cape Ann was in Rockport from December 1976 to January 1977; another was spotted during the same period in Salisbury. Both were adolescent birds. And the most recent recording of the bird's presence before that came in the 1940s, when two or three young gulls were seen on Cape Ann after a bout of bad weather, he said.

Leahy said the fact that the bird Trimble and others spotted this weekend is adult is a big deal, too — an adult has never been seen in this state.

"That this is such a pristine-looking bird is just icing on cake," he said.

"This is not a bird people can see by going somewhere nearby," he said. "It's something easily found only if you're at a weather station" in the Arctic Circle.

"This is exactly the kind of thing people come here to see," Leahy said, referring to the Cape Ann Chamber of Commerce's upcoming Birdwatching Weekend (see related box). "Hopefully, he hangs around."

It's the second sighting of an unusual bird in as many months. Just after Thanksgiving, an injured snowy owl, another visitor from the Arctic Circle, was found at the Heights at Cape Ann. In all, six snowy owls were counted Dec. 16 during the 79th annual Cape Ann Christmas Bird Count, a number that broke a 48-year-old record for the area.

It also wasn't the first sighting here of a rare gull. Renowned bird scientist and field guide author David Sibley first spotted a slaty-backed gull at Jodrey Fish Pier on Dec. 23, 2007, making the first identification of that bird in state history. Gloucester nearly lost that distinction to the Cape Cod town of Eastham, where a slaty-backed gull was spotted on the very same day, just an hour later.

This year's sightings have proven to be an exciting development for the birdwatching community, and many birders have flocked to Cape Ann hoping for a glimpse of the visitors.

Among those lucky enough to see the ivory gull Saturday was Phil Brown of Essex, who posted photos he took of the bird on his Web site, www.nebirdsplus.org.

"It was not on the list of birds I'd ever think to see," said Brown, who went to Eastern Point on a lunch break from work Saturday after a friend called him about the sighting.

"It was right there; I spent about 1âÑ2-hour spotting it," Brown said. "It flew to the cove, and then flew around quite a bit. Truly a beautiful little bird."

He said calling birding a hobby, for him, is an understatement. "It's a lot of fun, a lot good people," said Brown who combines his loves of birding and photography on his Web site.

After plowing for the past two days, Brown said he'll be using his day off today to try and catch another glimpse of the ivory gull.

The gull was sighted again Sunday and yesterday morning.

Ivory gulls, so named for their immaculate white body, tend to be shaped more like pigeons than the gulls usually spotted about Cape Ann. These medium-sized gulls grow to 17 inches long and weigh 1.4 pounds with a 37-inch wingspan.

Other signs that a birdwatcher is seeing a ivory gull are the bird's coal black eyes and feet and pale gray or blue bill tipped with pale yellow; the sexes appear the same. Immature birds look like adults but with variable amounts of black on the face and dark spots and smudges scattered over the body.

The North American breeding range of the ivory gull is restricted to a few sites in Arctic Canada. One population of these gulls winters just south of Greenland in the Labrador Sea. Another population winters in the Bering and Chukchi Seas. Ivory gulls concentrate where the ice meets the sea and at openings surrounded by sea ice called polynyas. Otherwise, the ivory gull breeds and winters at select locations around the Arctic Circle.

Andrea Holbrook may be contacted at aholbrook@gloucestertimes.com.

Save the date

What: Cape Ann Winter Birding Weekend

When: Jan. 30 to Feb. 1.

Who: The Cape Ann Chamber of Commerce, working with Massachusetts Audubon, is hosting the weekend and is seeking sponsors and exhibitors. Space is limited; preregistration by calling the chamber is recommended.

Where: Various locations.

Walk-in registration opens Friday, Jan. 30, at the Gloucester Elks at 3 p.m. Exhibitors will show products of interest to birders. There will be a reception from 5 to 7 p.m. Jim Barry, coordinator of Mass. Breeding Bird Atlas, will deliver an orientation on what birds participants are likely to see over the weekend.

On Saturday, Jan. 31, experts will lead tours at prime birding spots all over Cape Ann. By the end of the day, birders will have had a chance to visit all the spots. Following the tours, there will be dinner with keynote speaker Norman Smith. The director of Massachusetts Audubon's Blue Hills Trailside Museum and the Snowy Owl Project at Logan Airport will talk about owls, from the snowy owl, the largest, to the saw-whet owl, the tiniest.

On Sunday, Feb 1, weather permitting, birdwatchers will board 7 Seas Whale Watch's Privateer for either a trip to Stellwagen Bank Marine Sanctuary or around Cape Ann with Capt. Jay Frontiero.

How much: $10 registration; Saturday dinner, $50; Sunday cruise, $30.

Information: Judy Caulkett may be contacted at the Chamber, 978-283-1601, about sponsorships, exhibiting, or attending the weekend.