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If you’re a fan of big migrating birds, this is your time of year.

The Audubon Center at Riverlands in West Alton recently counted nearly 900 trumpeter swans, almost double last year’s number, and more eagles have been spotted in the area this winter too. One birder reported seeing 83 eagles on a recent drive on the Great River Road near Grafton.

Eagle Days — a prime event for enthusiasts of the birds of prey — will be held this weekend on the old Chain of Rocks Bridge. To top it off, the weather should be relatively mild; the high today is predicted to be 40, and on Sunday, 52.

“These birds give people a good excuse to get outside with a purpose,” said Pat Behle, a volunteer naturalist and part-time staffer at Columbia Bottoms Conservation Area in north St. Louis County.

On Thursday morning, several people viewed the birds at the Riverlands Migratory Bird Sanctuary in West Alton.

Kathy Vest, an internist from Godfrey, said she spent a lot of time running and fishing in the area, but her favorite activity was watching the swans.

“When the swans are here, I come out every day,” she said. “They’re so majestic. I tell everyone to come out and see them.”

Joe Anderson of Godfrey said he had taken thousands of photos of the eagles and swans. He works the afternoon shift at an archery shop, so he comes out to the sanctuary most mornings; the swans are his favorite wildlife to photograph.

“They’re just so pretty, and I like listening to them; it’s kind of a comforting sound,” he said of their call, which is similar to that of a French horn.

The trumpeter swans’ return may be the most impressive this winter. They are the largest waterfowl in North America, and in 2010 numbered 42,000 nationwide.

In 1991, officials at Riverlands saw just five of the birds, recognizable by a distinctive black bill. But this year they counted a record number, nearly 900, said Patricia Hagen, executive director of the Audubon Center at Riverlands.

The reasons for the influx over last year’s count of 500 include the bird’s successful breeding, its tendency to migrate to the same area and the managed wetlands at Riverlands, she said.

Even during the cold period when much of the Mississippi River was frozen, the Army Corps of Engineers was able to let water flow into Heron Pond, one of the larger ponds at the sanctuary, and Ellis Bay in front of the center had some open water in it as well.

“Between those two open water areas, the swans became very concentrated because they needed those areas for their resting period at night,” Hagen said.

The birds, most of which are from Iowa and Wisconsin, spend their winters here, arriving in late October and staying until late February, Hagen said.

Hagen said the birds felt safe in the habitat at the Riverlands because of the prairie that surrounds them, and the ponds have vegetation just below the surface they can eat. Corn and soybeans in nearby agricultural fields also provide food. The best times for viewing are before 9 a.m. and after 3:30 p.m.

The trumpeter swans usually mate for life and are very family-oriented, Hagen said.

“They’re magnificent, one of the most beautiful birds to see here at the sanctuary,” Hagen said. “People are just overwhelmed by them.”

Last weekend more than 2,000 people visited the center to see the swans and the eagles, which also are more plentiful this year because the colder winter is sending more of the birds farther south.

“Eagles are pretty opportunistic,” Hagen said. “They go where they have good food sources, so they move down the river as it ices up.”

Behl said trumpeter swans and eagles had been spotted at the old Chain of Rocks Bridge too, in part because the turbulent water with the rocks in the river keeps the water flowing there.

Thousands of people always come out this time of year to the bridge to see the eagles, she said. This weekend, Eagle Days is back after a one-year hiatus because of money problems.

The Missouri Department of Conservation and other groups will have a heating tent and viewing scopes as part of the activities, and the World Bird Sanctuary will have a live eagle on hand for an educational talk.

The big attraction, though, is the excellent vantage point from which to watch eagles soar, rest on ice floes and pluck fish from the water.

“This whole section of the river has a lot of activity,” Behl said.