Spring doesn't truly arrive in the northern states until the robins fly back from the South, and we see them hopping across lawns and hear them calling and singing from neighborhood trees.

For many people the sight of that first American robin, no matter the weather, means that spring is here. It's hard to know if American robins spotted in southern Minnesota in early March are migrants or birds that stayed through winter. A small percentage in Minnesota don't migrate but spend the winter in spots protected from cold winds, searching for leftover wild fruit, insects and other animal matter. Some don't survive. Don't be surprised to see them relishing the fruit from back-yard crabapple trees.

Migrating American robins are exceedingly flighty and noisy, and usually return in small- to medium-size flocks. For the past 14 years, on average, March 13 is the date for the first ones to return to the Twin Cities. These birds are all males. The first female robins return about a month later.

A male American robin has a black head with white eye-ring and a dark rusty-red breast; a female looks similar to a male but has a lighter gray head and pale reddish breast. Other than coloring, the only behavioral clues to distinguish the sexes are that the males sing and the females incubate eggs.

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.