About 312 species of birds are regularly seen in Minnesota each year, but that number drops to about 60 species during the winter. That means about 80 percent of Minnesota's bird population heads south for the winter each year. Sandpipers, warblers, wrens, vireos, thrushes, swallows and some hawks are among those making their trips now.

Insects and flower nectar will soon be scarce, so most ruby-throated hummingbirds will depart northern Minnesota by Sept. 12 and the southern part of the state by Sept. 25. Be sure to keep those sugar water feeders full, however, until you're certain the last of the hummers has left — it could be into October. Ruby-throats usually migrate by day but they can also migrate at night. Their wintering locations range from south Texas to Costa Rica.

On Sept. 15, 2003, a phenomenal 102,329 hawks were tallied as they flew and glided over Hawk Ridge in Duluth. It was the most hawks ever counted there in one day. The weather was warm and sunny, with a gentle westerly wind. About 99 percent of the migrants on that special day were broad-winged hawks. These birds often travel in huge wheeling flocks, known to hawk watchers as "kettles." The broad-winged hawk, about the size of a crow with a three-foot wingspread, nests in deciduous forest of the eastern United States and southern Canada. They winter in Central and South America.

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.