A martin is a bird in the swallow family that we won't see until April. And it's not to be confused with a marten, a mammal in the weasel family.

We need to be careful with the spelling. Pine martens are relatively unknown in Minnesota. They became rare by the late 1800s because of the value of their pelts and the ease with which they could be trapped.

When European explorers first came to Minnesota, the marten was a common animal in most of the forested areas in the northern half. Now they seem to be making a comeback in the northeast. I have seen pine martens twice, both times during the winter in the Arrowhead region.

Pine martens do best in boreal forests. They are active throughout the year and are thought of as a large, arboreal weasel about the size of a mink (2 feet long, 2 to 3 pounds). They are as comfortable in trees as squirrels are, and are tireless hunters in treetops, night or day. They are one of the few predators of squirrels, particularly the red squirrel. Largely nocturnal, pine martens favor hollow trees for making their dens. Mice make up the bulk of their diet.

Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.