Singing with trills and quavers is how a group of birds known as warblers got its name.

Warblers are small, chickadee-sized, often colorful songsters with slender, straight and pointed bills. Most inhabit woodlands, and about two dozen species migrate through the Twin Cities in waves starting this time of April and peaking in mid-May.

Since warblers feed on insects, they are highly migratory, and often thousands of miles can separate their winter and summer homes. They are largely nocturnal migrants whose long journeys in the dark over water and land expose them to many dangers. Warblers often strike radio towers, buildings and other obstructions with fatal results.

Years ago, as a young person trying to identify returning spring migrants in our Excelsior-area yard, I encountered dozens of quick-moving small birds in a single bur oak tree. I looked at their dazzling mix of bright yellow, gray, black and white, and listened to their cheerful trills suggesting the song of a junco. Looking in my "Peterson Field Guide," I felt great satisfaction in identifying them as myrtle warblers. Since that spring decades ago, we now call them yellow-rumped warblers, and I've enjoyed seeing and hearing them each year.

The yellow-rumped is the most common of the warblers in the Twin Cities area. No warbler is more easily recognized than this one, with four distinct patches of yellow on the crown, two sides and rump. They eat mainly insects in mid-spring, through summer and into fall, but during winter and on migration they can become fruit and seed eaters. This diet adaptation allows them to return early in spring, and a few have even lingered into a Minnesota winter. Yellow-rumped warblers nest in the spruce and fir forest in northeastern Minnesota and north into Canada.

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.