A series of twittering notes serve as the song of the barn swallow.

In southern Minnesota, we enjoy their musical chattering beginning about mid-April when they return from South America. We, too, can watch them glide with the ease and grace of Olympic figure skaters.

Strong and tireless fliers, they feed on Minnesota's flying insects, sometimes while in flight themselves.

The barn swallow nests across Eurasia and in much of North America. It's our state's most-familiar swallow and is spotted around much of Minnesota but for highly wooded areas. It is the only swallow with a deeply-forked tail. It is dark blue-black above, with a rusty throat and buff or pale rusty underparts.

The first barn swallow nests are built in May. Originally they nested on the rocky faces of cliffs, in caves, and sometimes attached their nests to tree trunks. But the species has long ago abandoned natural nest sites in favor of docks, bridges, barns and the eaves of other buildings. These are good spots for the half-cup shaped nest, fastened against an upright surface, built of mud pellets reinforced with grass and lined with feathers and fine grasses. Both sexes take part in constructing the nest, incubating the eggs, and caring for the young. Two broods of barn swallow young are raised each spring-summer nesting season.

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.