A reader wrote to ask about his recent sighting of a flying squirrel eating at one of his bird feeders. He didn't expect to see that mammal here.

Flying squirrels are resident in the Twin Cities area. There are two species, Northern Flying Squirrel and Southern, both occupying the northern two-thirds of the state, excepting western portions.

A couple of years ago we had a female raise her family here (Orono) in one of our nest boxes, built for bluebirds, but used in the yard by chickadees. We had them at our home east of Grantsburg, Wis., also, when we lived there in the 1990s.

Flying squirrels don't actually fly, but glide from one perch to another. They have a fold of skin, a membrane which extends from the front to the hind feet. Legs stretched form an airfoil that allows glides as long as 150 feet. Shorter glides are the rule.

The squirrels are about the size of chipmunks, with dense, glossy olive-brown fur above, white below, with large brown eyes. They eat — besides birdseed and suet — fruits, nuts, insects, small birds, and meat scraps.

Nocturnal, the squirrels are infrequently seen, feeders like those of my correspondent offering the best opportunities. The squirrels are beautiful animals, absolutely wonderful mind-their-own-business neighbors. Anyone who sees one is fortunate. Keep an eye on your feeder. (A neighborhood with mature trees helps). And if you have a cat, please keep it indoors at night.

Below, a flying squirrel at a feeder. If you look closely you can see the fold of skin used for gliding.