From the St. Petersburg Times:

They saw the first one just before Christmas: A lone robin lofting over their rooftop deck.

The bird was heading north, toward Mangrove Bay Golf Course. The next day, Lorraine Margeson said, she and her husband, Don, counted five robins as the sun set, swooping low and fast, flying in the same direction.

"There were 10 robins the next day, then 100, then 500," said Margeson, 52, who owns a computer networking company with her husband. "By the end of the week, we were seeing 100,000 or more every day."

They would fly out in the morning, just before dawn, heading south. In the evening they would come back, heading north. Eventually, it took more than two hours for the entire flock to pass overhead. "The whole sky just blanketed with red bellies, a wave rolling across the rooftops."

By the end of February, when the National Audubon Society co-sponsors its annual Great Backyard Bird Count, Margeson and other Tampa Bay birders had recorded 1.45 million robins over a four-day weekend — the largest winter roost in all of North America. In the rest of the U.S., only 400,321 robins were tallied.

"This is the third year in a row that St. Petersburg has held that record," said Pat Leonard of the Cornell Lab of Ornithology, which co-sponsors the backyard bird count. "Washington state had a big roost too recently. But the one in St. Petersburg seems to have taken on a life of its own."

John Ogden, a biology professor at the University of South Florida, said he has been watching the robins return to roost here for six years. Ogden's wife, Nancy, is on the board of the St. Petersburg Audubon Society. In late December, they start spending evenings near the eastern edge of 74th Avenue NE, on the western shore of Tampa Bay. They hike into a stand of low, thick mangroves.

"All of a sudden, just as the sun starts to go down, these robins come bombing out of the sky," Ogden said. "Thousands of them, all at once, diving into the trees. It's just amazing."

Robins don't build nests or rear young in Florida. They come, like all snowbirds, to avoid the cold — and eat fresh fruit. With the northern winter so much colder this year, and snow falling even in Texas, more robins than ever seemed to roost on a 10-acre tract between the golf course and Weedon Island Preserve.

Ogden said the birds' presence carries a message. "We need to be reminded, by these robins, how important it is to save even small spaces of wilderness. Look what a difference it makes."

The mangroves protect the robins from predators, Ogden said. Palm trees and Brazilian peppers provide plenty of berries. The 10-inch birds cover about 20 miles of ground a day, he said, foraging on land and in trees. And by squeezing into such a small space at night, more than a million robins crowded together, they keep each other warm until their plumage fluffs out and the rest of the country warms.

"Our million robins that we have here all fly north by early March — and will distribute all over the East Coast and Canada," Ogden said. By now, most of the flocks have probably broken up, he said, and some robins might have reached as far north as New York. "Soon, they'll be starting to sing, and by mid-May they'll be building nests."

Up north, the robins signal spring. Here in Florida, Margeson calls them her Christmas birds.