Nearly 50 years ago the well-known bird biologist and artist Roger Tory Peterson told our University of Minnesota Lake Itasca biology session field ornithology class that birds are the litmus paper of our environment.

What he meant was healthy birds with steady population numbers depend upon clean air and water, soil free of pollution, and healthy habitats. So do we humans.

As of September 2019, scientific studies showed that the number of wild birds in the United States and Canada had fallen by 29% since 1970. This is serious and should be a wake-up call. There are likely many causes for the bird loss, the most important of which includes habitat loss and wider use of pesticides. I truly enjoy the sight and sounds of the birds. Let us not keep moving toward a silent spring.

Currently, American robins are involved in nest building. Sexes can easily be told apart. The female has a paler back and breast and no black on the head. The selection of an appropriate site is just as important as nest construction. The site chosen and nest construction is handled primarily by the female. Nests are built about 5 to 20 feet above the ground. Sites on the ground itself or as high as 60 feet above ground are possible, but a firm foundation seems to be a more crucial requirement than concealment. The nest is supported mostly from below.

Mature orchard and shade trees and evergreens suit the robin's needs. Some robins nest in forests, but many are attracted to our yards and other city areas because of earthworm-filled lawns and gardens. Food always is a concern of nesting robins because their nestlings consume enormous amounts before they're independent.

Trees and shrubs are great places for nests, but some robins choose artificial sites like window ledges, rain pipes under eaves, fire escape steps, bridges, and fences.

American robins take five to six days to build a nest. The usual clutch size is four eggs over separate days. Blue in color, the eggs are incubated by the female for 12 to 14 days. Both parents feed the young, which leave the nest about 15 days after hatching.

Jim Gilbert's 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.