As the common loon is immortalized as the new emblem of Minnesota, the roughly 12,000 birds counted in the state's population aren't here to celebrate. They've gone fishing in the bathtub-warm waters of the Gulf of Mexico.

The icons of the North Woods spend about half their lives in the Deep South, but there are reasons they are more beloved here than off the Florida coasts.

To start, the birds change color so much during their southern months they can be hard to recognize. They lose their striking black-on-white plumage, which turns to more of a dull gray in winter. Their deep red eyes turn brown. Even their beaks change from a midnight black to light gray.

Loons can also be difficult to spot during their migration. In the fall they start to mass up on some of Minnesota's deepest and clearest lakes, rafting together by the hundreds to chase cisco and other fatty fish. Then they tend to fly to the middle of Lake Michigan, far out of sight, where they spend a few weeks packing on energy by hunting feeder fish and invasive round gobies, according to studies by the U.S. Geological Survey.

Once in Florida, they stay mostly quiet with no need to call for mates or fight for nesting territory. There are no young for the parents to carry on their backs. There are no small lakes that they have made their own. And even though they can dot Florida's shorelines and bays by the thousands, without their colors or distinctive calls, they can be hard to differentiate from the millions of other birds that shelter and winter in the south.

Loons have been relatively successful finding a mate and rearing their young in Minnesota since the 1990s. Annual surveys show that the population has stayed right around 12,000 over that time. But there are warning signs, said Krista Larson, a nongame research biologist for the Minnesota Department of Natural Resources.

The surveys show about a 0.5% drop each year in the number of chicks seen over the last 30 years, Larson said.

"That's a small decline — there are no alarm bells yet," she said. "But it's still a decline. We have to stay tuned to see if that juvenile recruitment piece might be dipping."

Come March and April, adult loons will get their colors back. The radar in their brains will kick on and the individual birds, which can live for 30 years, will find their home lake in Minnesota, returning to the same one out of 10,000-plus year after year. There, after six months of silence, they will let out their ancient mournful call.