Florida's attraction for retirees and vacationers extends across the nation's northern border, with Canadian "snowbirds" flocking to the Sunshine state each winter, according to a team of U.S. and Canadian population researchers.

While more than 800,000 native-born Canadians have become permanent U.S. residents, this country "is not necessarily an attractive place for Canadians to retire permanently," reported Charles F. Longino of the University of Miami.

But Canadian officials estimate that as many as 2 million of their citizens visit Florida each year. And many remain as long as six months, Longino said in an interview.

In many cases, Canadians vacationing in the United States have relatives and children in the states, Longino said. But, he said, they are often reluctant to make a permanent move because of the benefits of the Canadian national-health plan, which provides coverage as long as they live in Canada for six months of the year.

Indeed, many Canadians migrate as regularly as Canada geese, Longino joked, trekking between northern and southern homes within a few weeks of the six-month limitation.

Studies have found that it is common for Canadians to retire and sell their city residence but to keep a summer vacation home in the Muskoka Lakes "cottage country" north of Toronto and a winter home in Florida, Longino said.

A study presented to the Canadian Association of Gerontology last year, he said, disclosed several Canadian enclaves in Florida, notably near St. Petersburg, Port Charlotte, Lakeland, Winter Haven and Manatee, Lee and Collier counties.

Such concentrations provide social support for newcomers, Longino said, and he noted that an important aspect is the presence of many Canadian permanent residents of the United States.

A study of Canadians in Florida found that 2 percent had a child living permanently within 50 miles of their winter home, 8 percent had a brother or sister who lived nearby and 8 percent had other relatives residing within that area.

"Depending on the degree of overlap between these categories, there are from 8 to {nearly} 20 percent of the Canadian snowbirds who have family members living permanently in Florida and who are living close enough to provide an important part of their social environment while in the state," Longino reported.

Those permanent U.S. residents, natives of Canada, were profiled in a new study Longino presented recently at the annual scientific meeting of the Gerontological Society of America.

His report, "Native Canadians in the United States," was developed in cooperation with Victor W. Marshall of the University of Toronto, Larry C. Mullins of the University of South Florida and Richard D. Tucker of the University of Central Florida.

The 1980 U.S. Census counted 833,920 native Canadians living in the United States, about 39 percent of whom are 60 or older, the researchers found.