This year the first raft of American coots returned Sept. 18 to Lake Waconia for the fall season.

The gregarious coots reach their highest numbers on southern Minnesota lakes in late October, when it's not unusual to see them in rafts of more than 1,000. Coots will winter over in spots where there is open water and food available, but nearly all of them move south to open water — even to saltwater.

The American coot, also known as mud hen or mud duck, has a large range. It is found between Canada and northern parts of South America. Coots are present on our metro-area lakes in spring soon after the ice melts, but they are usually not seen here in the summer. Their slate-gray color; foot-long size; hen-like, conspicuous white bills; and greenish legs and long, big-lobed green feet make them easy to identify.

The necessity to patter over the water before they are airborne is another of distinctive characteristics. They are the most aquatic member of the rail family, are excellent swimmers and divers, and move in open water like ducks and often feed with them.

Coots graze on aquatic plants and also eat snails, insects and other small animals. Occasionally coots come up on land, and sometimes flocks can be seen far from water, feeding in meadows and on lawns. I have seen them grazing on Arizona golf courses in ­February.

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.